From 7a822c3120320bacbb77b41e0dd62ab84407a470 Mon Sep 17 00:00:00 2001
From: FBumann <117816358+FBumann@users.noreply.github.com>
Date: Sat, 15 Nov 2025 14:17:07 +0100
Subject: [PATCH 01/25] New lower case parameter names for flows in
 linear_converters.py

---
 flixopt/linear_converters.py | 347 ++++++++++++++++++++---------------
 1 file changed, 200 insertions(+), 147 deletions(-)

diff --git a/flixopt/linear_converters.py b/flixopt/linear_converters.py
index 046fcbd51..76aa25a47 100644
--- a/flixopt/linear_converters.py
+++ b/flixopt/linear_converters.py
@@ -34,11 +34,13 @@ class Boiler(LinearConverter):
         label: The label of the Element. Used to identify it in the FlowSystem.
         eta: Thermal efficiency factor (0-1 range). Defines the ratio of thermal
             output to fuel input energy content.
-        Q_fu: Fuel input-flow representing fuel consumption.
-        Q_th: Thermal output-flow representing heat generation.
+        fuel_flow: Fuel input-flow representing fuel consumption.
+        thermal_flow: Thermal output-flow representing heat generation.
         on_off_parameters: Parameters defining binary operation constraints and costs.
         meta_data: Used to store additional information. Not used internally but
             saved in results. Only use Python native types.
+        Q_fu: *Deprecated*. Use `fuel_flow` instead.
+        Q_th: *Deprecated*. Use `thermal_flow` instead.
 
     Examples:
         Natural gas boiler:
@@ -47,8 +49,8 @@ class Boiler(LinearConverter):
         gas_boiler = Boiler(
             label='natural_gas_boiler',
             eta=0.85,  # 85% thermal efficiency
-            Q_fu=natural_gas_flow,
-            Q_th=hot_water_flow,
+            fuel_flow=natural_gas_flow,
+            thermal_flow=hot_water_flow,
         )
         ```
 
@@ -58,8 +60,8 @@ class Boiler(LinearConverter):
         biomass_boiler = Boiler(
             label='wood_chip_boiler',
             eta=seasonal_efficiency_profile,  # Time-varying efficiency
-            Q_fu=biomass_flow,
-            Q_th=district_heat_flow,
+            fuel_flow=biomass_flow,
+            thermal_flow=district_heat_flow,
             on_off_parameters=OnOffParameters(
                 consecutive_on_hours_min=4,  # Minimum 4-hour operation
                 effects_per_switch_on={'startup_fuel': 50},  # Startup fuel penalty
@@ -68,7 +70,7 @@ class Boiler(LinearConverter):
         ```
 
     Note:
-        The conversion relationship is: Q_th = Q_fu × eta
+        The conversion relationship is: thermal_flow = fuel_flow × eta
 
         Efficiency should be between 0 and 1, where 1 represents perfect conversion
         (100% of fuel energy converted to useful thermal output).
@@ -78,30 +80,36 @@ def __init__(
         self,
         label: str,
         eta: Numeric_TPS,
-        Q_fu: Flow,
-        Q_th: Flow,
+        fuel_flow: Flow | None = None,
+        thermal_flow: Flow | None = None,
         on_off_parameters: OnOffParameters | None = None,
         meta_data: dict | None = None,
+        **kwargs,
     ):
+        # Handle deprecated parameters
+        fuel_flow = self._handle_deprecated_kwarg(kwargs, 'Q_fu', 'fuel_flow', fuel_flow)
+        thermal_flow = self._handle_deprecated_kwarg(kwargs, 'Q_th', 'thermal_flow', thermal_flow)
+        self._validate_kwargs(kwargs)
+
         super().__init__(
             label,
-            inputs=[Q_fu],
-            outputs=[Q_th],
-            conversion_factors=[{Q_fu.label: eta, Q_th.label: 1}],
+            inputs=[fuel_flow],
+            outputs=[thermal_flow],
             on_off_parameters=on_off_parameters,
             meta_data=meta_data,
         )
-        self.Q_fu = Q_fu
-        self.Q_th = Q_th
+        self.fuel_flow = fuel_flow
+        self.thermal_flow = thermal_flow
+        self.eta = eta  # Uses setter
 
     @property
     def eta(self):
-        return self.conversion_factors[0][self.Q_fu.label]
+        return self.conversion_factors[0][self.fuel_flow.label]
 
     @eta.setter
     def eta(self, value):
         check_bounds(value, 'eta', self.label_full, 0, 1)
-        self.conversion_factors[0][self.Q_fu.label] = value
+        self.conversion_factors = [{self.fuel_flow.label: value, self.thermal_flow.label: 1}]
 
 
 @register_class_for_io
@@ -119,11 +127,13 @@ class Power2Heat(LinearConverter):
         eta: Thermal efficiency factor (0-1 range). For resistance heating this is
             typically close to 1.0 (nearly 100% efficiency), but may be lower for
             electrode boilers or systems with distribution losses.
-        P_el: Electrical input-flow representing electricity consumption.
-        Q_th: Thermal output-flow representing heat generation.
+        power_flow: Electrical input-flow representing electricity consumption.
+        thermal_flow: Thermal output-flow representing heat generation.
         on_off_parameters: Parameters defining binary operation constraints and costs.
         meta_data: Used to store additional information. Not used internally but
             saved in results. Only use Python native types.
+        P_el: *Deprecated*. Use `power_flow` instead.
+        Q_th: *Deprecated*. Use `thermal_flow` instead.
 
     Examples:
         Electric resistance heater:
@@ -132,8 +142,8 @@ class Power2Heat(LinearConverter):
         electric_heater = Power2Heat(
             label='resistance_heater',
             eta=0.98,  # 98% efficiency (small losses)
-            P_el=electricity_flow,
-            Q_th=space_heating_flow,
+            power_flow=electricity_flow,
+            thermal_flow=space_heating_flow,
         )
         ```
 
@@ -143,8 +153,8 @@ class Power2Heat(LinearConverter):
         electrode_boiler = Power2Heat(
             label='electrode_steam_boiler',
             eta=0.95,  # 95% efficiency including boiler losses
-            P_el=industrial_electricity,
-            Q_th=process_steam_flow,
+            power_flow=industrial_electricity,
+            thermal_flow=process_steam_flow,
             on_off_parameters=OnOffParameters(
                 consecutive_on_hours_min=1,  # Minimum 1-hour operation
                 effects_per_switch_on={'startup_cost': 100},
@@ -153,7 +163,7 @@ class Power2Heat(LinearConverter):
         ```
 
     Note:
-        The conversion relationship is: Q_th = P_el × eta
+        The conversion relationship is: thermal_flow = power_flow × eta
 
         Unlike heat pumps, Power2Heat systems cannot exceed 100% efficiency (eta ≤ 1.0)
         as they only convert electrical energy without extracting additional energy
@@ -165,31 +175,37 @@ def __init__(
         self,
         label: str,
         eta: Numeric_TPS,
-        P_el: Flow,
-        Q_th: Flow,
+        power_flow: Flow | None = None,
+        thermal_flow: Flow | None = None,
         on_off_parameters: OnOffParameters | None = None,
         meta_data: dict | None = None,
+        **kwargs,
     ):
+        # Handle deprecated parameters
+        power_flow = self._handle_deprecated_kwarg(kwargs, 'P_el', 'power_flow', power_flow)
+        thermal_flow = self._handle_deprecated_kwarg(kwargs, 'Q_th', 'thermal_flow', thermal_flow)
+        self._validate_kwargs(kwargs)
+
         super().__init__(
             label,
-            inputs=[P_el],
-            outputs=[Q_th],
-            conversion_factors=[{P_el.label: eta, Q_th.label: 1}],
+            inputs=[power_flow],
+            outputs=[thermal_flow],
             on_off_parameters=on_off_parameters,
             meta_data=meta_data,
         )
 
-        self.P_el = P_el
-        self.Q_th = Q_th
+        self.power_flow = power_flow
+        self.thermal_flow = thermal_flow
+        self.eta = eta  # Uses setter
 
     @property
     def eta(self):
-        return self.conversion_factors[0][self.P_el.label]
+        return self.conversion_factors[0][self.power_flow.label]
 
     @eta.setter
     def eta(self, value):
         check_bounds(value, 'eta', self.label_full, 0, 1)
-        self.conversion_factors[0][self.P_el.label] = value
+        self.conversion_factors = [{self.power_flow.label: value, self.thermal_flow.label: 1}]
 
 
 @register_class_for_io
@@ -204,14 +220,17 @@ class HeatPump(LinearConverter):
 
     Args:
         label: The label of the Element. Used to identify it in the FlowSystem.
-        COP: Coefficient of Performance (typically 1-20 range). Defines the ratio of
+        cop: Coefficient of Performance (typically 1-20 range). Defines the ratio of
             thermal output to electrical input. COP > 1 indicates the heat pump extracts
             additional energy from the environment.
-        P_el: Electrical input-flow representing electricity consumption.
-        Q_th: Thermal output-flow representing heat generation.
+        power_flow: Electrical input-flow representing electricity consumption.
+        thermal_flow: Thermal output-flow representing heat generation.
         on_off_parameters: Parameters defining binary operation constraints and costs.
         meta_data: Used to store additional information. Not used internally but
             saved in results. Only use Python native types.
+        COP: *Deprecated*. Use `cop` instead.
+        P_el: *Deprecated*. Use `power_flow` instead.
+        Q_th: *Deprecated*. Use `thermal_flow` instead.
 
     Examples:
         Air-source heat pump with constant COP:
@@ -219,9 +238,9 @@ class HeatPump(LinearConverter):
         ```python
         air_hp = HeatPump(
             label='air_source_heat_pump',
-            COP=3.5,  # COP of 3.5 (350% efficiency)
-            P_el=electricity_flow,
-            Q_th=heating_flow,
+            cop=3.5,  # COP of 3.5 (350% efficiency)
+            power_flow=electricity_flow,
+            thermal_flow=heating_flow,
         )
         ```
 
@@ -230,9 +249,9 @@ class HeatPump(LinearConverter):
         ```python
         ground_hp = HeatPump(
             label='geothermal_heat_pump',
-            COP=temperature_dependent_cop,  # Time-varying COP based on ground temp
-            P_el=electricity_flow,
-            Q_th=radiant_heating_flow,
+            cop=temperature_dependent_cop,  # Time-varying COP based on ground temp
+            power_flow=electricity_flow,
+            thermal_flow=radiant_heating_flow,
             on_off_parameters=OnOffParameters(
                 consecutive_on_hours_min=2,  # Avoid frequent cycling
                 effects_per_running_hour={'maintenance': 0.5},
@@ -241,7 +260,7 @@ class HeatPump(LinearConverter):
         ```
 
     Note:
-        The conversion relationship is: Q_th = P_el × COP
+        The conversion relationship is: thermal_flow = power_flow × COP
 
         COP should be greater than 1 for realistic heat pump operation, with typical
         values ranging from 2-6 depending on technology and operating conditions.
@@ -251,32 +270,39 @@ class HeatPump(LinearConverter):
     def __init__(
         self,
         label: str,
-        COP: Numeric_TPS,
-        P_el: Flow,
-        Q_th: Flow,
+        cop: Numeric_TPS,
+        power_flow: Flow | None = None,
+        thermal_flow: Flow | None = None,
         on_off_parameters: OnOffParameters | None = None,
         meta_data: dict | None = None,
+        **kwargs,
     ):
+        # Handle deprecated parameters
+        power_flow = self._handle_deprecated_kwarg(kwargs, 'P_el', 'power_flow', power_flow)
+        thermal_flow = self._handle_deprecated_kwarg(kwargs, 'Q_th', 'thermal_flow', thermal_flow)
+        cop = self._handle_deprecated_kwarg(kwargs, 'COP', 'cop', cop)
+        self._validate_kwargs(kwargs)
+
         super().__init__(
             label,
-            inputs=[P_el],
-            outputs=[Q_th],
-            conversion_factors=[{P_el.label: COP, Q_th.label: 1}],
+            inputs=[power_flow],
+            outputs=[thermal_flow],
+            conversion_factors=[],
             on_off_parameters=on_off_parameters,
             meta_data=meta_data,
         )
-        self.P_el = P_el
-        self.Q_th = Q_th
-        self.COP = COP
+        self.power_flow = power_flow
+        self.thermal_flow = thermal_flow
+        self.cop = cop  # Uses setter
 
     @property
-    def COP(self):  # noqa: N802
-        return self.conversion_factors[0][self.P_el.label]
+    def cop(self):
+        return self.conversion_factors[0][self.power_flow.label]
 
-    @COP.setter
-    def COP(self, value):  # noqa: N802
-        check_bounds(value, 'COP', self.label_full, 1, 20)
-        self.conversion_factors[0][self.P_el.label] = value
+    @cop.setter
+    def cop(self, value):
+        check_bounds(value, 'cop', self.label_full, 1, 20)
+        self.conversion_factors = [{self.power_flow.label: value, self.thermal_flow.label: 1}]
 
 
 @register_class_for_io
@@ -294,11 +320,13 @@ class CoolingTower(LinearConverter):
         specific_electricity_demand: Auxiliary electricity demand per unit of cooling
             power (dimensionless, typically 0.01-0.05 range). Represents the fraction
             of thermal power that must be supplied as electricity for fans and pumps.
-        P_el: Electrical input-flow representing electricity consumption for fans/pumps.
-        Q_th: Thermal input-flow representing waste heat to be rejected to environment.
+        power_flow: Electrical input-flow representing electricity consumption for fans/pumps.
+        thermal_flow: Thermal input-flow representing waste heat to be rejected to environment.
         on_off_parameters: Parameters defining binary operation constraints and costs.
         meta_data: Used to store additional information. Not used internally but
             saved in results. Only use Python native types.
+        P_el: *Deprecated*. Use `power_flow` instead.
+        Q_th: *Deprecated*. Use `thermal_flow` instead.
 
     Examples:
         Industrial cooling tower:
@@ -307,8 +335,8 @@ class CoolingTower(LinearConverter):
         cooling_tower = CoolingTower(
             label='process_cooling_tower',
             specific_electricity_demand=0.025,  # 2.5% auxiliary power
-            P_el=cooling_electricity,
-            Q_th=waste_heat_flow,
+            power_flow=cooling_electricity,
+            thermal_flow=waste_heat_flow,
         )
         ```
 
@@ -318,8 +346,8 @@ class CoolingTower(LinearConverter):
         condenser_cooling = CoolingTower(
             label='power_plant_cooling',
             specific_electricity_demand=0.015,  # 1.5% auxiliary power
-            P_el=auxiliary_electricity,
-            Q_th=condenser_waste_heat,
+            power_flow=auxiliary_electricity,
+            thermal_flow=condenser_waste_heat,
             on_off_parameters=OnOffParameters(
                 consecutive_on_hours_min=4,  # Minimum operation time
                 effects_per_running_hour={'water_consumption': 2.5},  # m³/h
@@ -328,7 +356,7 @@ class CoolingTower(LinearConverter):
         ```
 
     Note:
-        The conversion relationship is: P_el = Q_th × specific_electricity_demand
+        The conversion relationship is: power_flow = thermal_flow × specific_electricity_demand
 
         The cooling tower consumes electrical power proportional to the thermal load.
         No thermal energy is produced - all thermal input is rejected to the environment.
@@ -341,33 +369,37 @@ def __init__(
         self,
         label: str,
         specific_electricity_demand: Numeric_TPS,
-        P_el: Flow,
-        Q_th: Flow,
+        power_flow: Flow | None = None,
+        thermal_flow: Flow | None = None,
         on_off_parameters: OnOffParameters | None = None,
         meta_data: dict | None = None,
+        **kwargs,
     ):
+        # Handle deprecated parameters
+        power_flow = self._handle_deprecated_kwarg(kwargs, 'P_el', 'power_flow', power_flow)
+        thermal_flow = self._handle_deprecated_kwarg(kwargs, 'Q_th', 'thermal_flow', thermal_flow)
+        self._validate_kwargs(kwargs)
+
         super().__init__(
             label,
-            inputs=[P_el, Q_th],
+            inputs=[power_flow, thermal_flow],
             outputs=[],
-            conversion_factors=[{P_el.label: -1, Q_th.label: specific_electricity_demand}],
             on_off_parameters=on_off_parameters,
             meta_data=meta_data,
         )
 
-        self.P_el = P_el
-        self.Q_th = Q_th
-
-        check_bounds(specific_electricity_demand, 'specific_electricity_demand', self.label_full, 0, 1)
+        self.power_flow = power_flow
+        self.thermal_flow = thermal_flow
+        self.specific_electricity_demand = specific_electricity_demand  # Uses setter
 
     @property
     def specific_electricity_demand(self):
-        return self.conversion_factors[0][self.Q_th.label]
+        return self.conversion_factors[0][self.thermal_flow.label]
 
     @specific_electricity_demand.setter
     def specific_electricity_demand(self, value):
         check_bounds(value, 'specific_electricity_demand', self.label_full, 0, 1)
-        self.conversion_factors[0][self.Q_th.label] = value
+        self.conversion_factors = [{self.power_flow.label: -1, self.thermal_flow.label: value}]
 
 
 @register_class_for_io
@@ -386,12 +418,15 @@ class CHP(LinearConverter):
             energy converted to useful thermal output.
         eta_el: Electrical efficiency factor (0-1 range). Defines the fraction of fuel
             energy converted to electrical output.
-        Q_fu: Fuel input-flow representing fuel consumption.
-        P_el: Electrical output-flow representing electricity generation.
-        Q_th: Thermal output-flow representing heat generation.
+        fuel_flow: Fuel input-flow representing fuel consumption.
+        power_flow: Electrical output-flow representing electricity generation.
+        thermal_flow: Thermal output-flow representing heat generation.
         on_off_parameters: Parameters defining binary operation constraints and costs.
         meta_data: Used to store additional information. Not used internally but
             saved in results. Only use Python native types.
+        Q_fu: *Deprecated*. Use `fuel_flow` instead.
+        P_el: *Deprecated*. Use `power_flow` instead.
+        Q_th: *Deprecated*. Use `thermal_flow` instead.
 
     Examples:
         Natural gas CHP unit:
@@ -401,9 +436,9 @@ class CHP(LinearConverter):
             label='natural_gas_chp',
             eta_th=0.45,  # 45% thermal efficiency
             eta_el=0.35,  # 35% electrical efficiency (80% total)
-            Q_fu=natural_gas_flow,
-            P_el=electricity_flow,
-            Q_th=district_heat_flow,
+            fuel_flow=natural_gas_flow,
+            power_flow=electricity_flow,
+            thermal_flow=district_heat_flow,
         )
         ```
 
@@ -414,9 +449,9 @@ class CHP(LinearConverter):
             label='industrial_chp',
             eta_th=0.40,
             eta_el=0.38,
-            Q_fu=fuel_gas_flow,
-            P_el=plant_electricity,
-            Q_th=process_steam,
+            fuel_flow=fuel_gas_flow,
+            power_flow=plant_electricity,
+            thermal_flow=process_steam,
             on_off_parameters=OnOffParameters(
                 consecutive_on_hours_min=8,  # Minimum 8-hour operation
                 effects_per_switch_on={'startup_cost': 5000},
@@ -427,8 +462,8 @@ class CHP(LinearConverter):
 
     Note:
         The conversion relationships are:
-        - Q_th = Q_fu × eta_th (thermal output)
-        - P_el = Q_fu × eta_el (electrical output)
+        - thermal_flow = fuel_flow × eta_th (thermal output)
+        - power_flow = fuel_flow × eta_el (electrical output)
 
         Total efficiency (eta_th + eta_el) should be ≤ 1.0, with typical combined
         efficiencies of 80-90% for modern CHP units. This provides significant
@@ -440,47 +475,61 @@ def __init__(
         label: str,
         eta_th: Numeric_TPS,
         eta_el: Numeric_TPS,
-        Q_fu: Flow,
-        P_el: Flow,
-        Q_th: Flow,
+        fuel_flow: Flow | None = None,
+        power_flow: Flow | None = None,
+        thermal_flow: Flow | None = None,
         on_off_parameters: OnOffParameters | None = None,
         meta_data: dict | None = None,
+        **kwargs,
     ):
-        heat = {Q_fu.label: eta_th, Q_th.label: 1}
-        electricity = {Q_fu.label: eta_el, P_el.label: 1}
+        # Handle deprecated parameters
+        fuel_flow = self._handle_deprecated_kwarg(kwargs, 'Q_fu', 'fuel_flow', fuel_flow)
+        power_flow = self._handle_deprecated_kwarg(kwargs, 'P_el', 'power_flow', power_flow)
+        thermal_flow = self._handle_deprecated_kwarg(kwargs, 'Q_th', 'thermal_flow', thermal_flow)
+        self._validate_kwargs(kwargs)
 
         super().__init__(
             label,
-            inputs=[Q_fu],
-            outputs=[Q_th, P_el],
-            conversion_factors=[heat, electricity],
+            inputs=[fuel_flow],
+            outputs=[thermal_flow, power_flow],
+            conversion_factors=[],
             on_off_parameters=on_off_parameters,
             meta_data=meta_data,
         )
 
-        self.Q_fu = Q_fu
-        self.P_el = P_el
-        self.Q_th = Q_th
+        self.fuel_flow = fuel_flow
+        self.power_flow = power_flow
+        self.thermal_flow = thermal_flow
+        self.eta_th = eta_th  # Uses setter
+        self.eta_el = eta_el  # Uses setter
 
         check_bounds(eta_el + eta_th, 'eta_th+eta_el', self.label_full, 0, 1)
 
     @property
     def eta_th(self):
-        return self.conversion_factors[0][self.Q_fu.label]
+        return self.conversion_factors[0][self.fuel_flow.label]
 
     @eta_th.setter
     def eta_th(self, value):
         check_bounds(value, 'eta_th', self.label_full, 0, 1)
-        self.conversion_factors[0][self.Q_fu.label] = value
+        if len(self.conversion_factors) < 2:
+            # Initialize structure if not yet set
+            self.conversion_factors = [{self.fuel_flow.label: value, self.thermal_flow.label: 1}, {}]
+        else:
+            self.conversion_factors[0] = {self.fuel_flow.label: value, self.thermal_flow.label: 1}
 
     @property
     def eta_el(self):
-        return self.conversion_factors[1][self.Q_fu.label]
+        return self.conversion_factors[1][self.fuel_flow.label]
 
     @eta_el.setter
     def eta_el(self, value):
         check_bounds(value, 'eta_el', self.label_full, 0, 1)
-        self.conversion_factors[1][self.Q_fu.label] = value
+        if len(self.conversion_factors) < 2:
+            # Initialize structure if not yet set
+            self.conversion_factors = [{}, {self.fuel_flow.label: value, self.power_flow.label: 1}]
+        else:
+            self.conversion_factors[1] = {self.fuel_flow.label: value, self.power_flow.label: 1}
 
 
 @register_class_for_io
@@ -495,16 +544,20 @@ class HeatPumpWithSource(LinearConverter):
 
     Args:
         label: The label of the Element. Used to identify it in the FlowSystem.
-        COP: Coefficient of Performance (typically 1-20 range). Defines the ratio of
+        cop: Coefficient of Performance (typically 1-20 range). Defines the ratio of
             thermal output to electrical input. The heat source extraction is automatically
-            calculated as Q_ab = Q_th × (COP-1)/COP.
-        P_el: Electrical input-flow representing electricity consumption for compressor.
-        Q_ab: Heat source input-flow representing thermal energy extracted from environment
+            calculated as heat_source_flow = thermal_flow × (COP-1)/COP.
+        power_flow: Electrical input-flow representing electricity consumption for compressor.
+        heat_source_flow: Heat source input-flow representing thermal energy extracted from environment
             (ground, air, water source).
-        Q_th: Thermal output-flow representing useful heat delivered to the application.
+        thermal_flow: Thermal output-flow representing useful heat delivered to the application.
         on_off_parameters: Parameters defining binary operation constraints and costs.
         meta_data: Used to store additional information. Not used internally but
             saved in results. Only use Python native types.
+        COP: *Deprecated*. Use `cop` instead.
+        P_el: *Deprecated*. Use `power_flow` instead.
+        Q_ab: *Deprecated*. Use `heat_source_flow` instead.
+        Q_th: *Deprecated*. Use `thermal_flow` instead.
 
     Examples:
         Ground-source heat pump with explicit ground coupling:
@@ -512,10 +565,10 @@ class HeatPumpWithSource(LinearConverter):
         ```python
         ground_source_hp = HeatPumpWithSource(
             label='geothermal_heat_pump',
-            COP=4.5,  # High COP due to stable ground temperature
-            P_el=electricity_flow,
-            Q_ab=ground_heat_extraction,  # Heat extracted from ground loop
-            Q_th=building_heating_flow,
+            cop=4.5,  # High COP due to stable ground temperature
+            power_flow=electricity_flow,
+            heat_source_flow=ground_heat_extraction,  # Heat extracted from ground loop
+            thermal_flow=building_heating_flow,
         )
         ```
 
@@ -524,10 +577,10 @@ class HeatPumpWithSource(LinearConverter):
         ```python
         waste_heat_pump = HeatPumpWithSource(
             label='waste_heat_pump',
-            COP=temperature_dependent_cop,  # Varies with temperature of heat source
-            P_el=electricity_consumption,
-            Q_ab=industrial_heat_extraction,  # Heat extracted from a industrial process or waste water
-            Q_th=heat_supply,
+            cop=temperature_dependent_cop,  # Varies with temperature of heat source
+            power_flow=electricity_consumption,
+            heat_source_flow=industrial_heat_extraction,  # Heat extracted from a industrial process or waste water
+            thermal_flow=heat_supply,
             on_off_parameters=OnOffParameters(
                 consecutive_on_hours_min=0.5,  # 30-minute minimum runtime
                 effects_per_switch_on={'costs': 1000},
@@ -537,9 +590,9 @@ class HeatPumpWithSource(LinearConverter):
 
     Note:
         The conversion relationships are:
-        - Q_th = P_el × COP (thermal output from electrical input)
-        - Q_ab = Q_th × (COP-1)/COP (heat source extraction)
-        - Energy balance: Q_th = P_el + Q_ab
+        - thermal_flow = power_flow × COP (thermal output from electrical input)
+        - heat_source_flow = thermal_flow × (COP-1)/COP (heat source extraction)
+        - Energy balance: thermal_flow = power_flow + heat_source_flow
 
         This formulation explicitly tracks the heat source, which is
         important for systems where the source capacity or temperature is limited,
@@ -552,40 +605,46 @@ class HeatPumpWithSource(LinearConverter):
     def __init__(
         self,
         label: str,
-        COP: Numeric_TPS,
-        P_el: Flow,
-        Q_ab: Flow,
-        Q_th: Flow,
+        cop: Numeric_TPS,
+        power_flow: Flow | None = None,
+        heat_source_flow: Flow | None = None,
+        thermal_flow: Flow | None = None,
         on_off_parameters: OnOffParameters | None = None,
         meta_data: dict | None = None,
+        **kwargs,
     ):
+        # Handle deprecated parameters
+        power_flow = self._handle_deprecated_kwarg(kwargs, 'P_el', 'power_flow', power_flow)
+        heat_source_flow = self._handle_deprecated_kwarg(kwargs, 'Q_ab', 'heat_source_flow', heat_source_flow)
+        thermal_flow = self._handle_deprecated_kwarg(kwargs, 'Q_th', 'thermal_flow', thermal_flow)
+        cop = self._handle_deprecated_kwarg(kwargs, 'COP', 'cop', cop)
+        self._validate_kwargs(kwargs)
+
         super().__init__(
             label,
-            inputs=[P_el, Q_ab],
-            outputs=[Q_th],
-            conversion_factors=[{P_el.label: COP, Q_th.label: 1}, {Q_ab.label: COP / (COP - 1), Q_th.label: 1}],
+            inputs=[power_flow, heat_source_flow],
+            outputs=[thermal_flow],
+            conversion_factors=[],
             on_off_parameters=on_off_parameters,
             meta_data=meta_data,
         )
-        self.P_el = P_el
-        self.Q_ab = Q_ab
-        self.Q_th = Q_th
-
-        if np.any(np.asarray(self.COP) <= 1):
-            raise ValueError(f'{self.label_full}.COP must be strictly > 1 for HeatPumpWithSource.')
+        self.power_flow = power_flow
+        self.heat_source_flow = heat_source_flow
+        self.thermal_flow = thermal_flow
+        self.cop = cop  # Uses setter
 
     @property
-    def COP(self):  # noqa: N802
-        return self.conversion_factors[0][self.P_el.label]
+    def cop(self):  # noqa: N802
+        return self.conversion_factors[0][self.power_flow.label]
 
-    @COP.setter
-    def COP(self, value):  # noqa: N802
-        check_bounds(value, 'COP', self.label_full, 1, 20)
+    @cop.setter
+    def cop(self, value):  # noqa: N802
+        check_bounds(value, 'cop', self.label_full, 1, 20)
         if np.any(np.asarray(value) <= 1):
-            raise ValueError(f'{self.label_full}.COP must be strictly > 1 for HeatPumpWithSource.')
+            raise ValueError(f'{self.label_full}.cop must be strictly > 1 for HeatPumpWithSource.')
         self.conversion_factors = [
-            {self.P_el.label: value, self.Q_th.label: 1},
-            {self.Q_ab.label: value / (value - 1), self.Q_th.label: 1},
+            {self.power_flow.label: value, self.thermal_flow.label: 1},
+            {self.heat_source_flow.label: value / (value - 1), self.thermal_flow.label: 1},
         ]
 
 
@@ -612,19 +671,13 @@ def check_bounds(
         lower_bound = lower_bound.data
     if isinstance(upper_bound, TimeSeriesData):
         upper_bound = upper_bound.data
-
-    # Convert to NumPy arrays to handle xr.DataArray, pd.Series, pd.DataFrame
-    value_arr = np.asarray(value)
-    lower_arr = np.asarray(lower_bound)
-    upper_arr = np.asarray(upper_bound)
-
-    if not np.all(value_arr > lower_arr):
+    if not np.all(value > lower_bound):
         logger.warning(
             f"'{element_label}.{parameter_label}' is equal or below the common lower bound {lower_bound}."
-            f'    {parameter_label}.min={np.min(value_arr)};    {parameter_label}={value}'
+            f'    {parameter_label}.min={np.min(value)};    {parameter_label}={value}'
         )
-    if not np.all(value_arr < upper_arr):
+    if not np.all(value < upper_bound):
         logger.warning(
             f"'{element_label}.{parameter_label}' exceeds or matches the common upper bound {upper_bound}."
-            f'    {parameter_label}.max={np.max(value_arr)};    {parameter_label}={value}'
+            f'    {parameter_label}.max={np.max(value)};    {parameter_label}={value}'
         )

From bcead8afcf0aff3f9ac23dc5b72862a1a71bdb93 Mon Sep 17 00:00:00 2001
From: FBumann <117816358+FBumann@users.noreply.github.com>
Date: Sat, 15 Nov 2025 14:22:14 +0100
Subject: [PATCH 02/25] Improve setting of conversion factors

---
 flixopt/linear_converters.py | 23 +++++++----------------
 1 file changed, 7 insertions(+), 16 deletions(-)

diff --git a/flixopt/linear_converters.py b/flixopt/linear_converters.py
index 76aa25a47..b5bdb5169 100644
--- a/flixopt/linear_converters.py
+++ b/flixopt/linear_converters.py
@@ -492,7 +492,7 @@ def __init__(
             label,
             inputs=[fuel_flow],
             outputs=[thermal_flow, power_flow],
-            conversion_factors=[],
+            conversion_factors=[{}, {}],
             on_off_parameters=on_off_parameters,
             meta_data=meta_data,
         )
@@ -512,11 +512,7 @@ def eta_th(self):
     @eta_th.setter
     def eta_th(self, value):
         check_bounds(value, 'eta_th', self.label_full, 0, 1)
-        if len(self.conversion_factors) < 2:
-            # Initialize structure if not yet set
-            self.conversion_factors = [{self.fuel_flow.label: value, self.thermal_flow.label: 1}, {}]
-        else:
-            self.conversion_factors[0] = {self.fuel_flow.label: value, self.thermal_flow.label: 1}
+        self.conversion_factors[0] = {self.fuel_flow.label: value, self.thermal_flow.label: 1}
 
     @property
     def eta_el(self):
@@ -525,11 +521,7 @@ def eta_el(self):
     @eta_el.setter
     def eta_el(self, value):
         check_bounds(value, 'eta_el', self.label_full, 0, 1)
-        if len(self.conversion_factors) < 2:
-            # Initialize structure if not yet set
-            self.conversion_factors = [{}, {self.fuel_flow.label: value, self.power_flow.label: 1}]
-        else:
-            self.conversion_factors[1] = {self.fuel_flow.label: value, self.power_flow.label: 1}
+        self.conversion_factors[1] = {self.fuel_flow.label: value, self.power_flow.label: 1}
 
 
 @register_class_for_io
@@ -624,7 +616,6 @@ def __init__(
             label,
             inputs=[power_flow, heat_source_flow],
             outputs=[thermal_flow],
-            conversion_factors=[],
             on_off_parameters=on_off_parameters,
             meta_data=meta_data,
         )
@@ -634,14 +625,14 @@ def __init__(
         self.cop = cop  # Uses setter
 
     @property
-    def cop(self):  # noqa: N802
+    def cop(self):
         return self.conversion_factors[0][self.power_flow.label]
 
     @cop.setter
-    def cop(self, value):  # noqa: N802
+    def cop(self, value):
         check_bounds(value, 'cop', self.label_full, 1, 20)
-        if np.any(np.asarray(value) <= 1):
-            raise ValueError(f'{self.label_full}.cop must be strictly > 1 for HeatPumpWithSource.')
+        if np.any(np.asarray(value) == 1):
+            raise ValueError(f'{self.label_full}.cop must be strictly !=1 for HeatPumpWithSource.')
         self.conversion_factors = [
             {self.power_flow.label: value, self.thermal_flow.label: 1},
             {self.heat_source_flow.label: value / (value - 1), self.thermal_flow.label: 1},

From b45618bf9f6f4b6ab8e6a7a537111722dc875eb1 Mon Sep 17 00:00:00 2001
From: FBumann <117816358+FBumann@users.noreply.github.com>
Date: Sat, 15 Nov 2025 14:25:07 +0100
Subject: [PATCH 03/25] Add deprectaed parameter access

---
 flixopt/linear_converters.py | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/flixopt/linear_converters.py b/flixopt/linear_converters.py
index b5bdb5169..c1dfd66e3 100644
--- a/flixopt/linear_converters.py
+++ b/flixopt/linear_converters.py
@@ -5,6 +5,7 @@
 from __future__ import annotations
 
 import logging
+import warnings
 from typing import TYPE_CHECKING
 
 import numpy as np
@@ -638,6 +639,15 @@ def cop(self, value):
             {self.heat_source_flow.label: value / (value - 1), self.thermal_flow.label: 1},
         ]
 
+    @property
+    def Q_th(self) -> Flow:  # noqa: N802
+        warnings.warn(
+            'The "Q_th" property is deprecated. Use "thermal_flow" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return self.thermal_flow
+
 
 def check_bounds(
     value: Numeric_TPS,

From 46f8f6c9100f9ab7d0cc9961bd774d6727d6177e Mon Sep 17 00:00:00 2001
From: FBumann <117816358+FBumann@users.noreply.github.com>
Date: Sat, 15 Nov 2025 14:30:51 +0100
Subject: [PATCH 04/25] Add deprectaed parameter access

---
 flixopt/linear_converters.py | 135 +++++++++++++++++++++++++++++++++++
 1 file changed, 135 insertions(+)

diff --git a/flixopt/linear_converters.py b/flixopt/linear_converters.py
index c1dfd66e3..8b96f9185 100644
--- a/flixopt/linear_converters.py
+++ b/flixopt/linear_converters.py
@@ -112,6 +112,24 @@ def eta(self, value):
         check_bounds(value, 'eta', self.label_full, 0, 1)
         self.conversion_factors = [{self.fuel_flow.label: value, self.thermal_flow.label: 1}]
 
+    @property
+    def Q_fu(self) -> Flow:  # noqa: N802
+        warnings.warn(
+            'The "Q_fu" property is deprecated. Use "fuel_flow" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return self.fuel_flow
+
+    @property
+    def Q_th(self) -> Flow:  # noqa: N802
+        warnings.warn(
+            'The "Q_th" property is deprecated. Use "thermal_flow" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return self.thermal_flow
+
 
 @register_class_for_io
 class Power2Heat(LinearConverter):
@@ -208,6 +226,24 @@ def eta(self, value):
         check_bounds(value, 'eta', self.label_full, 0, 1)
         self.conversion_factors = [{self.power_flow.label: value, self.thermal_flow.label: 1}]
 
+    @property
+    def P_el(self) -> Flow:  # noqa: N802
+        warnings.warn(
+            'The "P_el" property is deprecated. Use "power_flow" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return self.power_flow
+
+    @property
+    def Q_th(self) -> Flow:  # noqa: N802
+        warnings.warn(
+            'The "Q_th" property is deprecated. Use "thermal_flow" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return self.thermal_flow
+
 
 @register_class_for_io
 class HeatPump(LinearConverter):
@@ -305,6 +341,33 @@ def cop(self, value):
         check_bounds(value, 'cop', self.label_full, 1, 20)
         self.conversion_factors = [{self.power_flow.label: value, self.thermal_flow.label: 1}]
 
+    @property
+    def COP(self) -> Numeric_TPS:  # noqa: N802
+        warnings.warn(
+            'The "COP" property is deprecated. Use "cop" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return self.cop
+
+    @property
+    def P_el(self) -> Flow:  # noqa: N802
+        warnings.warn(
+            'The "P_el" property is deprecated. Use "power_flow" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return self.power_flow
+
+    @property
+    def Q_th(self) -> Flow:  # noqa: N802
+        warnings.warn(
+            'The "Q_th" property is deprecated. Use "thermal_flow" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return self.thermal_flow
+
 
 @register_class_for_io
 class CoolingTower(LinearConverter):
@@ -402,6 +465,24 @@ def specific_electricity_demand(self, value):
         check_bounds(value, 'specific_electricity_demand', self.label_full, 0, 1)
         self.conversion_factors = [{self.power_flow.label: -1, self.thermal_flow.label: value}]
 
+    @property
+    def P_el(self) -> Flow:  # noqa: N802
+        warnings.warn(
+            'The "P_el" property is deprecated. Use "power_flow" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return self.power_flow
+
+    @property
+    def Q_th(self) -> Flow:  # noqa: N802
+        warnings.warn(
+            'The "Q_th" property is deprecated. Use "thermal_flow" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return self.thermal_flow
+
 
 @register_class_for_io
 class CHP(LinearConverter):
@@ -524,6 +605,33 @@ def eta_el(self, value):
         check_bounds(value, 'eta_el', self.label_full, 0, 1)
         self.conversion_factors[1] = {self.fuel_flow.label: value, self.power_flow.label: 1}
 
+    @property
+    def Q_fu(self) -> Flow:  # noqa: N802
+        warnings.warn(
+            'The "Q_fu" property is deprecated. Use "fuel_flow" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return self.fuel_flow
+
+    @property
+    def P_el(self) -> Flow:  # noqa: N802
+        warnings.warn(
+            'The "P_el" property is deprecated. Use "power_flow" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return self.power_flow
+
+    @property
+    def Q_th(self) -> Flow:  # noqa: N802
+        warnings.warn(
+            'The "Q_th" property is deprecated. Use "thermal_flow" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return self.thermal_flow
+
 
 @register_class_for_io
 class HeatPumpWithSource(LinearConverter):
@@ -639,6 +747,33 @@ def cop(self, value):
             {self.heat_source_flow.label: value / (value - 1), self.thermal_flow.label: 1},
         ]
 
+    @property
+    def COP(self) -> Numeric_TPS:  # noqa: N802
+        warnings.warn(
+            'The "COP" property is deprecated. Use "cop" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return self.cop
+
+    @property
+    def P_el(self) -> Flow:  # noqa: N802
+        warnings.warn(
+            'The "P_el" property is deprecated. Use "power_flow" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return self.power_flow
+
+    @property
+    def Q_ab(self) -> Flow:  # noqa: N802
+        warnings.warn(
+            'The "Q_ab" property is deprecated. Use "heat_source_flow" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return self.heat_source_flow
+
     @property
     def Q_th(self) -> Flow:  # noqa: N802
         warnings.warn(

From b1f6f6c4ccf9930b6792a3a9a4ff4980216d04f8 Mon Sep 17 00:00:00 2001
From: FBumann <117816358+FBumann@users.noreply.github.com>
Date: Sat, 15 Nov 2025 14:32:12 +0100
Subject: [PATCH 05/25] Update CHANGELOG.md

---
 CHANGELOG.md | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index bd11fb442..40bf00825 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -70,8 +70,17 @@ If upgrading from v2.x, see the [v3.0.0 release notes](https://github.com/flixOp
 ### ♻️ Changed
 - **Code structure**: Removed `commons.py` module and moved all imports directly to `__init__.py` for cleaner code organization (no public API changes)
 - **Type handling improvements**: Updated internal data handling to work seamlessly with the new type system
+- **Parameter renaming in `linear_converters.py`**: Renamed parameters to use lowercase, descriptive names for better consistency:
+    - `Boiler`: `Q_fu` → `fuel_flow`, `Q_th` → `thermal_flow`
+    - `Power2Heat`: `P_el` → `power_flow`, `Q_th` → `thermal_flow`
+    - `HeatPump`: `COP` → `cop`, `P_el` → `power_flow`, `Q_th` → `thermal_flow`
+    - `CoolingTower`: `P_el` → `power_flow`, `Q_th` → `thermal_flow`
+    - `CHP`: `Q_fu` → `fuel_flow`, `P_el` → `power_flow`, `Q_th` → `thermal_flow`
+    - `HeatPumpWithSource`: `COP` → `cop`, `P_el` → `power_flow`, `Q_ab` → `heat_source_flow`, `Q_th` → `thermal_flow`
 
 ### 🗑️ Deprecated
+- **Old parameter names in `linear_converters.py`**: The old uppercase parameter names are now deprecated and accessible as properties that emit `DeprecationWarning`. They will be removed in v4.0.0:
+    - `Q_fu`, `Q_th`, `P_el`, `COP`, `Q_ab` (use lowercase equivalents instead)
 
 ### 🔥 Removed
 

From 59f82cc2be6bfc022a62e70d7573f04c8b64b239 Mon Sep 17 00:00:00 2001
From: FBumann <117816358+FBumann@users.noreply.github.com>
Date: Sat, 15 Nov 2025 15:11:36 +0100
Subject: [PATCH 06/25] Add setters

---
 flixopt/linear_converters.py | 170 +++++++++++++++++++++++++++++++++--
 1 file changed, 165 insertions(+), 5 deletions(-)

diff --git a/flixopt/linear_converters.py b/flixopt/linear_converters.py
index 8b96f9185..cb7595ccf 100644
--- a/flixopt/linear_converters.py
+++ b/flixopt/linear_converters.py
@@ -121,6 +121,15 @@ def Q_fu(self) -> Flow:  # noqa: N802
         )
         return self.fuel_flow
 
+    @Q_fu.setter
+    def Q_fu(self, value: Flow) -> None:  # noqa: N802
+        warnings.warn(
+            'The "Q_fu" property is deprecated. Use "fuel_flow" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        self.fuel_flow = value
+
     @property
     def Q_th(self) -> Flow:  # noqa: N802
         warnings.warn(
@@ -130,6 +139,15 @@ def Q_th(self) -> Flow:  # noqa: N802
         )
         return self.thermal_flow
 
+    @Q_th.setter
+    def Q_th(self, value: Flow) -> None:  # noqa: N802
+        warnings.warn(
+            'The "Q_th" property is deprecated. Use "thermal_flow" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        self.thermal_flow = value
+
 
 @register_class_for_io
 class Power2Heat(LinearConverter):
@@ -235,6 +253,15 @@ def P_el(self) -> Flow:  # noqa: N802
         )
         return self.power_flow
 
+    @P_el.setter
+    def P_el(self, value: Flow) -> None:  # noqa: N802
+        warnings.warn(
+            'The "P_el" property is deprecated. Use "power_flow" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        self.power_flow = value
+
     @property
     def Q_th(self) -> Flow:  # noqa: N802
         warnings.warn(
@@ -244,6 +271,15 @@ def Q_th(self) -> Flow:  # noqa: N802
         )
         return self.thermal_flow
 
+    @Q_th.setter
+    def Q_th(self, value: Flow) -> None:  # noqa: N802
+        warnings.warn(
+            'The "Q_th" property is deprecated. Use "thermal_flow" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        self.thermal_flow = value
+
 
 @register_class_for_io
 class HeatPump(LinearConverter):
@@ -350,6 +386,15 @@ def COP(self) -> Numeric_TPS:  # noqa: N802
         )
         return self.cop
 
+    @COP.setter
+    def COP(self, value: Numeric_TPS) -> None:  # noqa: N802
+        warnings.warn(
+            'The "COP" property is deprecated. Use "cop" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        self.cop = value
+
     @property
     def P_el(self) -> Flow:  # noqa: N802
         warnings.warn(
@@ -359,6 +404,15 @@ def P_el(self) -> Flow:  # noqa: N802
         )
         return self.power_flow
 
+    @P_el.setter
+    def P_el(self, value: Flow) -> None:  # noqa: N802
+        warnings.warn(
+            'The "P_el" property is deprecated. Use "power_flow" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        self.power_flow = value
+
     @property
     def Q_th(self) -> Flow:  # noqa: N802
         warnings.warn(
@@ -368,6 +422,15 @@ def Q_th(self) -> Flow:  # noqa: N802
         )
         return self.thermal_flow
 
+    @Q_th.setter
+    def Q_th(self, value: Flow) -> None:  # noqa: N802
+        warnings.warn(
+            'The "Q_th" property is deprecated. Use "thermal_flow" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        self.thermal_flow = value
+
 
 @register_class_for_io
 class CoolingTower(LinearConverter):
@@ -474,6 +537,15 @@ def P_el(self) -> Flow:  # noqa: N802
         )
         return self.power_flow
 
+    @P_el.setter
+    def P_el(self, value: Flow) -> None:  # noqa: N802
+        warnings.warn(
+            'The "P_el" property is deprecated. Use "power_flow" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        self.power_flow = value
+
     @property
     def Q_th(self) -> Flow:  # noqa: N802
         warnings.warn(
@@ -483,6 +555,15 @@ def Q_th(self) -> Flow:  # noqa: N802
         )
         return self.thermal_flow
 
+    @Q_th.setter
+    def Q_th(self, value: Flow) -> None:  # noqa: N802
+        warnings.warn(
+            'The "Q_th" property is deprecated. Use "thermal_flow" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        self.thermal_flow = value
+
 
 @register_class_for_io
 class CHP(LinearConverter):
@@ -614,6 +695,15 @@ def Q_fu(self) -> Flow:  # noqa: N802
         )
         return self.fuel_flow
 
+    @Q_fu.setter
+    def Q_fu(self, value: Flow) -> None:  # noqa: N802
+        warnings.warn(
+            'The "Q_fu" property is deprecated. Use "fuel_flow" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        self.fuel_flow = value
+
     @property
     def P_el(self) -> Flow:  # noqa: N802
         warnings.warn(
@@ -623,6 +713,15 @@ def P_el(self) -> Flow:  # noqa: N802
         )
         return self.power_flow
 
+    @P_el.setter
+    def P_el(self, value: Flow) -> None:  # noqa: N802
+        warnings.warn(
+            'The "P_el" property is deprecated. Use "power_flow" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        self.power_flow = value
+
     @property
     def Q_th(self) -> Flow:  # noqa: N802
         warnings.warn(
@@ -632,6 +731,15 @@ def Q_th(self) -> Flow:  # noqa: N802
         )
         return self.thermal_flow
 
+    @Q_th.setter
+    def Q_th(self, value: Flow) -> None:  # noqa: N802
+        warnings.warn(
+            'The "Q_th" property is deprecated. Use "thermal_flow" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        self.thermal_flow = value
+
 
 @register_class_for_io
 class HeatPumpWithSource(LinearConverter):
@@ -740,7 +848,9 @@ def cop(self):
     @cop.setter
     def cop(self, value):
         check_bounds(value, 'cop', self.label_full, 1, 20)
-        if np.any(np.asarray(value) == 1):
+        # Unwrap TimeSeriesData before numpy comparison (consistent with check_bounds)
+        ts_value = value.data if isinstance(value, TimeSeriesData) else value
+        if np.any(np.asarray(ts_value) == 1):
             raise ValueError(f'{self.label_full}.cop must be strictly !=1 for HeatPumpWithSource.')
         self.conversion_factors = [
             {self.power_flow.label: value, self.thermal_flow.label: 1},
@@ -756,6 +866,15 @@ def COP(self) -> Numeric_TPS:  # noqa: N802
         )
         return self.cop
 
+    @COP.setter
+    def COP(self, value: Numeric_TPS) -> None:  # noqa: N802
+        warnings.warn(
+            'The "COP" property is deprecated. Use "cop" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        self.cop = value
+
     @property
     def P_el(self) -> Flow:  # noqa: N802
         warnings.warn(
@@ -765,6 +884,15 @@ def P_el(self) -> Flow:  # noqa: N802
         )
         return self.power_flow
 
+    @P_el.setter
+    def P_el(self, value: Flow) -> None:  # noqa: N802
+        warnings.warn(
+            'The "P_el" property is deprecated. Use "power_flow" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        self.power_flow = value
+
     @property
     def Q_ab(self) -> Flow:  # noqa: N802
         warnings.warn(
@@ -774,6 +902,15 @@ def Q_ab(self) -> Flow:  # noqa: N802
         )
         return self.heat_source_flow
 
+    @Q_ab.setter
+    def Q_ab(self, value: Flow) -> None:  # noqa: N802
+        warnings.warn(
+            'The "Q_ab" property is deprecated. Use "heat_source_flow" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        self.heat_source_flow = value
+
     @property
     def Q_th(self) -> Flow:  # noqa: N802
         warnings.warn(
@@ -783,6 +920,15 @@ def Q_th(self) -> Flow:  # noqa: N802
         )
         return self.thermal_flow
 
+    @Q_th.setter
+    def Q_th(self, value: Flow) -> None:  # noqa: N802
+        warnings.warn(
+            'The "Q_th" property is deprecated. Use "thermal_flow" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        self.thermal_flow = value
+
 
 def check_bounds(
     value: Numeric_TPS,
@@ -807,13 +953,27 @@ def check_bounds(
         lower_bound = lower_bound.data
     if isinstance(upper_bound, TimeSeriesData):
         upper_bound = upper_bound.data
+
+    # Convert to array for shape and statistics
+    value_arr = np.asarray(value)
+
     if not np.all(value > lower_bound):
+        # Log shape and statistics instead of full array to avoid verbose output
+        if value_arr.size > 1:
+            value_info = f'shape={value_arr.shape}, min={np.min(value)}'
+        else:
+            value_info = f'{value}'
         logger.warning(
-            f"'{element_label}.{parameter_label}' is equal or below the common lower bound {lower_bound}."
-            f'    {parameter_label}.min={np.min(value)};    {parameter_label}={value}'
+            f"'{element_label}.{parameter_label}' is equal or below the common lower bound {lower_bound}. "
+            f'{parameter_label}: {value_info}'
         )
     if not np.all(value < upper_bound):
+        # Log shape and statistics instead of full array to avoid verbose output
+        if value_arr.size > 1:
+            value_info = f'shape={value_arr.shape}, max={np.max(value)}'
+        else:
+            value_info = f'{value}'
         logger.warning(
-            f"'{element_label}.{parameter_label}' exceeds or matches the common upper bound {upper_bound}."
-            f'    {parameter_label}.max={np.max(value)};    {parameter_label}={value}'
+            f"'{element_label}.{parameter_label}' exceeds or matches the common upper bound {upper_bound}. "
+            f'{parameter_label}: {value_info}'
         )

From 8a46d03f465c7b5eba3adf4f946027d25a0a8f13 Mon Sep 17 00:00:00 2001
From: FBumann <117816358+FBumann@users.noreply.github.com>
Date: Sat, 15 Nov 2025 16:20:30 +0100
Subject: [PATCH 07/25] Merge from main

---
 CHANGELOG.md                                  |  11 +-
 docs/getting-started.md                       |  18 +
 examples/02_Complex/complex_example.py        |   3 +-
 .../two_stage_optimization.py                 |   4 +-
 flixopt/aggregation.py                        |   6 +-
 flixopt/calculation.py                        |  18 +-
 flixopt/color_processing.py                   |   5 +-
 flixopt/components.py                         |   4 +-
 flixopt/config.py                             | 473 ++++--------------
 flixopt/core.py                               |   4 +-
 flixopt/effects.py                            |   4 +-
 flixopt/elements.py                           |   8 +-
 flixopt/features.py                           |   3 -
 flixopt/flow_system.py                        |   4 +-
 flixopt/interface.py                          |   5 +-
 flixopt/io.py                                 |   8 +-
 flixopt/modeling.py                           |   5 +-
 flixopt/network_app.py                        |   5 +-
 flixopt/plotting.py                           |   4 +-
 flixopt/results.py                            |  14 +-
 flixopt/solvers.py                            |   5 +-
 flixopt/structure.py                          |   7 +-
 pyproject.toml                                |   2 +-
 tests/test_config.py                          | 223 +++++----
 24 files changed, 298 insertions(+), 545 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 40bf00825..833ddd3c0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -51,7 +51,7 @@ If upgrading from v2.x, see the [v3.0.0 release notes](https://github.com/flixOp
 
 ## [Unreleased] - ????-??-??
 
-**Summary**: Type system overhaul with comprehensive type hints for better IDE support and code clarity.
+**Summary**: Type system overhaul and migration to loguru for logging
 
 If upgrading from v2.x, see the [v3.0.0 release notes](https://github.com/flixOpt/flixOpt/releases/tag/v3.0.0) and [Migration Guide](https://flixopt.github.io/flixopt/latest/user-guide/migration-guide-v3/).
 
@@ -64,8 +64,13 @@ If upgrading from v2.x, see the [v3.0.0 release notes](https://github.com/flixOp
     - Added `Scalar` type for scalar-only numeric values
     - Added `NumericOrBool` utility type for internal use
     - Type system supports scalars, numpy arrays, pandas Series/DataFrames, and xarray DataArrays
+- Lazy logging evaluation - expensive log operations only execute when log level is active
+- `CONFIG.Logging.verbose_tracebacks` option for detailed debugging with variable values
 
 ### 💥 Breaking Changes
+- **Logging framework**: Migrated to [loguru](https://loguru.readthedocs.io/)
+    - Removed `CONFIG.Logging` parameters: `rich`, `Colors`, `date_format`, `format`, `console_width`, `show_path`, `show_logger_name`
+    - For advanced formatting, use loguru's API directly after `CONFIG.apply()`
 
 ### ♻️ Changed
 - **Code structure**: Removed `commons.py` module and moved all imports directly to `__init__.py` for cleaner code organization (no public API changes)
@@ -92,13 +97,15 @@ If upgrading from v2.x, see the [v3.0.0 release notes](https://github.com/flixOp
 
 ### 📦 Dependencies
 - Updated `mkdocs-material` to v9.6.23
+- Replaced `rich >= 13.0.0` with `loguru >= 0.7.0` for logging
 
 ### 📝 Docs
 - Enhanced documentation in `flixopt/types.py` with comprehensive examples and dimension explanation table
 - Clarified Effect type docstrings - Effect types are dicts, but single numeric values work through union types
 - Added clarifying comments in `effects.py` explaining parameter handling and transformation
 - Improved OnOffParameters attribute documentation
-
+- Updated getting-started guide with loguru examples
+- Updated `config.py` docstrings for loguru integration
 
 ### 👷 Development
 - Added test for FlowSystem resampling
diff --git a/docs/getting-started.md b/docs/getting-started.md
index 044ffb872..5841de3a4 100644
--- a/docs/getting-started.md
+++ b/docs/getting-started.md
@@ -22,6 +22,24 @@ For all features including interactive network visualizations and time series ag
 pip install "flixopt[full]"
 ```
 
+## Logging
+
+FlixOpt uses [loguru](https://loguru.readthedocs.io/) for logging. Logging is silent by default but can be easily configured. For beginners, use our internal convenience methods. Experts can use loguru directly.
+
+```python
+from flixopt import CONFIG
+
+# Enable console logging
+CONFIG.Logging.console = True
+CONFIG.Logging.level = 'INFO'
+CONFIG.apply()
+
+# Or use a preset configuration for exploring
+CONFIG.exploring()
+```
+
+For more details on logging configuration, see the [`CONFIG.Logging`][flixopt.config.CONFIG.Logging] documentation.
+
 ## Basic Workflow
 
 Working with FlixOpt follows a general pattern:
diff --git a/examples/02_Complex/complex_example.py b/examples/02_Complex/complex_example.py
index b8ef76a03..3ff5b251c 100644
--- a/examples/02_Complex/complex_example.py
+++ b/examples/02_Complex/complex_example.py
@@ -4,7 +4,6 @@
 
 import numpy as np
 import pandas as pd
-from rich.pretty import pprint  # Used for pretty printing
 
 import flixopt as fx
 
@@ -188,7 +187,7 @@
     flow_system.add_elements(Costs, CO2, PE, Gaskessel, Waermelast, Gasbezug, Stromverkauf, speicher)
     flow_system.add_elements(bhkw_2) if use_chp_with_piecewise_conversion else flow_system.add_elements(bhkw)
 
-    pprint(flow_system)  # Get a string representation of the FlowSystem
+    print(flow_system)  # Get a string representation of the FlowSystem
     try:
         flow_system.start_network_app()  # Start the network app
     except ImportError as e:
diff --git a/examples/05_Two-stage-optimization/two_stage_optimization.py b/examples/05_Two-stage-optimization/two_stage_optimization.py
index 9647e803c..7354cb877 100644
--- a/examples/05_Two-stage-optimization/two_stage_optimization.py
+++ b/examples/05_Two-stage-optimization/two_stage_optimization.py
@@ -7,17 +7,15 @@
 While the final optimum might differ from the global optimum, the solving will be much faster.
 """
 
-import logging
 import pathlib
 import timeit
 
 import pandas as pd
 import xarray as xr
+from loguru import logger
 
 import flixopt as fx
 
-logger = logging.getLogger('flixopt')
-
 if __name__ == '__main__':
     fx.CONFIG.exploring()
 
diff --git a/flixopt/aggregation.py b/flixopt/aggregation.py
index cd0fdde3c..99b13bd45 100644
--- a/flixopt/aggregation.py
+++ b/flixopt/aggregation.py
@@ -6,12 +6,12 @@
 from __future__ import annotations
 
 import copy
-import logging
 import pathlib
 import timeit
 from typing import TYPE_CHECKING
 
 import numpy as np
+from loguru import logger
 
 try:
     import tsam.timeseriesaggregation as tsam
@@ -37,8 +37,6 @@
     from .elements import Component
     from .flow_system import FlowSystem
 
-logger = logging.getLogger('flixopt')
-
 
 class Aggregation:
     """
@@ -106,7 +104,7 @@ def cluster(self) -> None:
         self.aggregated_data = self.tsam.predictOriginalData()
 
         self.clustering_duration_seconds = timeit.default_timer() - start_time  # Zeit messen:
-        logger.info(self.describe_clusters())
+        logger.opt(lazy=True).info('{result}', result=lambda: self.describe_clusters())
 
     def describe_clusters(self) -> str:
         description = {}
diff --git a/flixopt/calculation.py b/flixopt/calculation.py
index 1125da401..64c589e3a 100644
--- a/flixopt/calculation.py
+++ b/flixopt/calculation.py
@@ -10,7 +10,6 @@
 
 from __future__ import annotations
 
-import logging
 import math
 import pathlib
 import sys
@@ -20,6 +19,7 @@
 from typing import TYPE_CHECKING, Annotated, Any
 
 import numpy as np
+from loguru import logger
 from tqdm import tqdm
 
 from . import io as fx_io
@@ -39,8 +39,6 @@
     from .solvers import _Solver
     from .structure import FlowSystemModel
 
-logger = logging.getLogger('flixopt')
-
 
 class Calculation:
     """
@@ -238,7 +236,7 @@ def solve(
             **solver.options,
         )
         self.durations['solving'] = round(timeit.default_timer() - t_start, 2)
-        logger.info(f'Model solved with {solver.name} in {self.durations["solving"]:.2f} seconds.')
+        logger.success(f'Model solved with {solver.name} in {self.durations["solving"]:.2f} seconds.')
         logger.info(f'Model status after solve: {self.model.status}')
 
         if self.model.status == 'warning':
@@ -255,12 +253,10 @@ def solve(
         # Log the formatted output
         should_log = log_main_results if log_main_results is not None else CONFIG.Solving.log_main_results
         if should_log:
-            logger.info(
-                f'{" Main Results ":#^80}\n'
-                + fx_io.format_yaml_string(
-                    self.main_results,
-                    compact_numeric_lists=True,
-                )
+            logger.opt(lazy=True).info(
+                '{result}',
+                result=lambda: f'{" Main Results ":#^80}\n'
+                + fx_io.format_yaml_string(self.main_results, compact_numeric_lists=True),
             )
 
         self.results = CalculationResults.from_calculation(self)
@@ -673,7 +669,7 @@ def do_modeling_and_solve(
             for key, value in calc.durations.items():
                 self.durations[key] += value
 
-        logger.info(f'Model solved with {solver.name} in {self.durations["solving"]:.2f} seconds.')
+        logger.success(f'Model solved with {solver.name} in {self.durations["solving"]:.2f} seconds.')
 
         self.results = SegmentedCalculationResults.from_calculation(self)
 
diff --git a/flixopt/color_processing.py b/flixopt/color_processing.py
index 2959acc82..9d874e027 100644
--- a/flixopt/color_processing.py
+++ b/flixopt/color_processing.py
@@ -6,15 +6,12 @@
 
 from __future__ import annotations
 
-import logging
-
 import matplotlib.colors as mcolors
 import matplotlib.pyplot as plt
 import plotly.express as px
+from loguru import logger
 from plotly.exceptions import PlotlyError
 
-logger = logging.getLogger('flixopt')
-
 
 def _rgb_string_to_hex(color: str) -> str:
     """Convert Plotly RGB/RGBA string format to hex.
diff --git a/flixopt/components.py b/flixopt/components.py
index 6a5abfc4e..c51b4b7d2 100644
--- a/flixopt/components.py
+++ b/flixopt/components.py
@@ -4,12 +4,12 @@
 
 from __future__ import annotations
 
-import logging
 import warnings
 from typing import TYPE_CHECKING, Literal
 
 import numpy as np
 import xarray as xr
+from loguru import logger
 
 from . import io as fx_io
 from .core import PlausibilityError
@@ -25,8 +25,6 @@
     from .flow_system import FlowSystem
     from .types import Numeric_PS, Numeric_TPS
 
-logger = logging.getLogger('flixopt')
-
 
 @register_class_for_io
 class LinearConverter(Component):
diff --git a/flixopt/config.py b/flixopt/config.py
index d7ea824d9..07d7e24a9 100644
--- a/flixopt/config.py
+++ b/flixopt/config.py
@@ -1,23 +1,16 @@
 from __future__ import annotations
 
-import logging
 import os
 import sys
 import warnings
-from logging.handlers import RotatingFileHandler
 from pathlib import Path
 from types import MappingProxyType
 from typing import Literal
 
-from rich.console import Console
-from rich.logging import RichHandler
-from rich.style import Style
-from rich.theme import Theme
+from loguru import logger
 
 __all__ = ['CONFIG', 'change_logging_level']
 
-logger = logging.getLogger('flixopt')
-
 
 # SINGLE SOURCE OF TRUTH - immutable to prevent accidental modification
 _DEFAULTS = MappingProxyType(
@@ -27,24 +20,10 @@
             {
                 'level': 'INFO',
                 'file': None,
-                'rich': False,
                 'console': False,
                 'max_file_size': 10_485_760,  # 10MB
                 'backup_count': 5,
-                'date_format': '%Y-%m-%d %H:%M:%S',
-                'format': '%(message)s',
-                'console_width': 120,
-                'show_path': False,
-                'show_logger_name': False,
-                'colors': MappingProxyType(
-                    {
-                        'DEBUG': '\033[90m',  # Bright Black/Gray
-                        'INFO': '\033[0m',  # Default/White
-                        'WARNING': '\033[33m',  # Yellow
-                        'ERROR': '\033[31m',  # Red
-                        'CRITICAL': '\033[1m\033[31m',  # Bold Red
-                    }
-                ),
+                'verbose_tracebacks': False,
             }
         ),
         'modeling': MappingProxyType(
@@ -81,6 +60,9 @@ class CONFIG:
 
     Always call ``CONFIG.apply()`` after changes.
 
+    Note:
+        flixopt uses `loguru <https://loguru.readthedocs.io/>`_ for logging.
+
     Attributes:
         Logging: Logging configuration.
         Modeling: Optimization modeling parameters.
@@ -114,86 +96,48 @@ class Logging:
         Silent by default. Enable via ``console=True`` or ``file='path'``.
 
         Attributes:
-            level: Logging level.
-            file: Log file path for file logging.
-            console: Enable console output.
-            rich: Use Rich library for enhanced output.
-            max_file_size: Max file size before rotation.
+            level: Logging level (DEBUG, INFO, SUCCESS, WARNING, ERROR, CRITICAL).
+            file: Log file path for file logging (None to disable).
+            console: Enable console output (True/'stdout' or 'stderr').
+            max_file_size: Max file size in bytes before rotation.
             backup_count: Number of backup files to keep.
-            date_format: Date/time format string.
-            format: Log message format string.
-            console_width: Console width for Rich handler.
-            show_path: Show file paths in messages.
-            show_logger_name: Show logger name in messages.
-            Colors: ANSI color codes for log levels.
+            verbose_tracebacks: Show detailed tracebacks with variable values.
 
         Examples:
             ```python
+            # Enable console logging
+            CONFIG.Logging.console = True
+            CONFIG.Logging.level = 'DEBUG'
+            CONFIG.apply()
+
             # File logging with rotation
             CONFIG.Logging.file = 'app.log'
             CONFIG.Logging.max_file_size = 5_242_880  # 5MB
             CONFIG.apply()
 
-            # Rich handler with stdout
-            CONFIG.Logging.console = True  # or 'stdout'
-            CONFIG.Logging.rich = True
-            CONFIG.apply()
-
-            # Console output to stderr
+            # Console to stderr
             CONFIG.Logging.console = 'stderr'
             CONFIG.apply()
             ```
+
+        Note:
+            For advanced formatting or custom loguru configuration,
+            use loguru's API directly after calling CONFIG.apply():
+
+            ```python
+            from loguru import logger
+
+            CONFIG.apply()  # Basic setup
+            logger.add('custom.log', format='{time} {message}')
+            ```
         """
 
-        level: Literal['DEBUG', 'INFO', 'WARNING', 'ERROR', 'CRITICAL'] = _DEFAULTS['logging']['level']
+        level: Literal['DEBUG', 'INFO', 'SUCCESS', 'WARNING', 'ERROR', 'CRITICAL'] = _DEFAULTS['logging']['level']
         file: str | None = _DEFAULTS['logging']['file']
-        rich: bool = _DEFAULTS['logging']['rich']
         console: bool | Literal['stdout', 'stderr'] = _DEFAULTS['logging']['console']
         max_file_size: int = _DEFAULTS['logging']['max_file_size']
         backup_count: int = _DEFAULTS['logging']['backup_count']
-        date_format: str = _DEFAULTS['logging']['date_format']
-        format: str = _DEFAULTS['logging']['format']
-        console_width: int = _DEFAULTS['logging']['console_width']
-        show_path: bool = _DEFAULTS['logging']['show_path']
-        show_logger_name: bool = _DEFAULTS['logging']['show_logger_name']
-
-        class Colors:
-            """ANSI color codes for log levels.
-
-            Attributes:
-                DEBUG: ANSI color for DEBUG level.
-                INFO: ANSI color for INFO level.
-                WARNING: ANSI color for WARNING level.
-                ERROR: ANSI color for ERROR level.
-                CRITICAL: ANSI color for CRITICAL level.
-
-            Examples:
-                ```python
-                CONFIG.Logging.Colors.INFO = '\\033[32m'  # Green
-                CONFIG.Logging.Colors.ERROR = '\\033[1m\\033[31m'  # Bold red
-                CONFIG.apply()
-                ```
-
-            Common ANSI codes:
-                - '\\033[30m' - Black
-                - '\\033[31m' - Red
-                - '\\033[32m' - Green
-                - '\\033[33m' - Yellow
-                - '\\033[34m' - Blue
-                - '\\033[35m' - Magenta
-                - '\\033[36m' - Cyan
-                - '\\033[37m' - White
-                - '\\033[90m' - Bright Black/Gray
-                - '\\033[0m' - Reset to default
-                - '\\033[1m\\033[3Xm' - Bold (replace X with color code 0-7)
-                - '\\033[2m\\033[3Xm' - Dim (replace X with color code 0-7)
-            """
-
-            DEBUG: str = _DEFAULTS['logging']['colors']['DEBUG']
-            INFO: str = _DEFAULTS['logging']['colors']['INFO']
-            WARNING: str = _DEFAULTS['logging']['colors']['WARNING']
-            ERROR: str = _DEFAULTS['logging']['colors']['ERROR']
-            CRITICAL: str = _DEFAULTS['logging']['colors']['CRITICAL']
+        verbose_tracebacks: bool = _DEFAULTS['logging']['verbose_tracebacks']
 
     class Modeling:
         """Optimization modeling parameters.
@@ -274,12 +218,7 @@ class Plotting:
     def reset(cls):
         """Reset all configuration values to defaults."""
         for key, value in _DEFAULTS['logging'].items():
-            if key == 'colors':
-                # Reset nested Colors class
-                for color_key, color_value in value.items():
-                    setattr(cls.Logging.Colors, color_key, color_value)
-            else:
-                setattr(cls.Logging, key, value)
+            setattr(cls.Logging, key, value)
 
         for key, value in _DEFAULTS['modeling'].items():
             setattr(cls.Modeling, key, value)
@@ -296,15 +235,7 @@ def reset(cls):
     @classmethod
     def apply(cls):
         """Apply current configuration to logging system."""
-        # Convert Colors class attributes to dict
-        colors_dict = {
-            'DEBUG': cls.Logging.Colors.DEBUG,
-            'INFO': cls.Logging.Colors.INFO,
-            'WARNING': cls.Logging.Colors.WARNING,
-            'ERROR': cls.Logging.Colors.ERROR,
-            'CRITICAL': cls.Logging.Colors.CRITICAL,
-        }
-        valid_levels = list(colors_dict)
+        valid_levels = ['DEBUG', 'INFO', 'SUCCESS', 'WARNING', 'ERROR', 'CRITICAL']
         if cls.Logging.level.upper() not in valid_levels:
             raise ValueError(f"Invalid log level '{cls.Logging.level}'. Must be one of: {', '.join(valid_levels)}")
 
@@ -320,16 +251,10 @@ def apply(cls):
         _setup_logging(
             default_level=cls.Logging.level,
             log_file=cls.Logging.file,
-            use_rich_handler=cls.Logging.rich,
             console=cls.Logging.console,
             max_file_size=cls.Logging.max_file_size,
             backup_count=cls.Logging.backup_count,
-            date_format=cls.Logging.date_format,
-            format=cls.Logging.format,
-            console_width=cls.Logging.console_width,
-            show_path=cls.Logging.show_path,
-            show_logger_name=cls.Logging.show_logger_name,
-            colors=colors_dict,
+            verbose_tracebacks=cls.Logging.verbose_tracebacks,
         )
 
     @classmethod
@@ -364,11 +289,7 @@ def _apply_config_dict(cls, config_dict: dict):
         for key, value in config_dict.items():
             if key == 'logging' and isinstance(value, dict):
                 for nested_key, nested_value in value.items():
-                    if nested_key == 'colors' and isinstance(nested_value, dict):
-                        # Handle nested colors under logging
-                        for color_key, color_value in nested_value.items():
-                            setattr(cls.Logging.Colors, color_key, color_value)
-                    else:
+                    if hasattr(cls.Logging, nested_key):
                         setattr(cls.Logging, nested_key, nested_value)
             elif key == 'modeling' and isinstance(value, dict):
                 for nested_key, nested_value in value.items():
@@ -394,22 +315,10 @@ def to_dict(cls) -> dict:
             'logging': {
                 'level': cls.Logging.level,
                 'file': cls.Logging.file,
-                'rich': cls.Logging.rich,
                 'console': cls.Logging.console,
                 'max_file_size': cls.Logging.max_file_size,
                 'backup_count': cls.Logging.backup_count,
-                'date_format': cls.Logging.date_format,
-                'format': cls.Logging.format,
-                'console_width': cls.Logging.console_width,
-                'show_path': cls.Logging.show_path,
-                'show_logger_name': cls.Logging.show_logger_name,
-                'colors': {
-                    'DEBUG': cls.Logging.Colors.DEBUG,
-                    'INFO': cls.Logging.Colors.INFO,
-                    'WARNING': cls.Logging.Colors.WARNING,
-                    'ERROR': cls.Logging.Colors.ERROR,
-                    'CRITICAL': cls.Logging.Colors.CRITICAL,
-                },
+                'verbose_tracebacks': cls.Logging.verbose_tracebacks,
             },
             'modeling': {
                 'big': cls.Modeling.big,
@@ -451,11 +360,12 @@ def silent(cls) -> type[CONFIG]:
     def debug(cls) -> type[CONFIG]:
         """Configure for debug mode with verbose output.
 
-        Enables console logging at DEBUG level and all solver output for
-        troubleshooting. Automatically calls apply().
+        Enables console logging at DEBUG level, verbose tracebacks,
+        and all solver output for troubleshooting. Automatically calls apply().
         """
         cls.Logging.console = True
         cls.Logging.level = 'DEBUG'
+        cls.Logging.verbose_tracebacks = True
         cls.Solving.log_to_console = True
         cls.Solving.log_main_results = True
         cls.apply()
@@ -497,274 +407,106 @@ def browser_plotting(cls) -> type[CONFIG]:
         return cls
 
 
-class MultilineFormatter(logging.Formatter):
-    """Formatter that handles multi-line messages with consistent prefixes.
+def _format_multiline(record):
+    """Format multi-line messages with box-style borders for better readability.
 
-    Args:
-        fmt: Log message format string.
-        datefmt: Date/time format string.
-        show_logger_name: Show logger name in log messages.
-    """
-
-    def __init__(self, fmt: str = '%(message)s', datefmt: str | None = None, show_logger_name: bool = False):
-        super().__init__(fmt=fmt, datefmt=datefmt)
-        self.show_logger_name = show_logger_name
-
-    def format(self, record) -> str:
-        record.message = record.getMessage()
-        message_lines = self._style.format(record).split('\n')
-        timestamp = self.formatTime(record, self.datefmt)
-        log_level = record.levelname.ljust(8)
-
-        if self.show_logger_name:
-            # Truncate long logger names for readability
-            logger_name = record.name if len(record.name) <= 20 else f'...{record.name[-17:]}'
-            log_prefix = f'{timestamp} | {log_level} | {logger_name.ljust(20)} |'
-        else:
-            log_prefix = f'{timestamp} | {log_level} |'
-
-        indent = ' ' * (len(log_prefix) + 1)  # +1 for the space after prefix
+    Single-line messages use standard format.
+    Multi-line messages use boxed format with ┌─, │, └─ characters.
 
-        lines = [f'{log_prefix} {message_lines[0]}']
-        if len(message_lines) > 1:
-            lines.extend([f'{indent}{line}' for line in message_lines[1:]])
-
-        return '\n'.join(lines)
-
-
-class ColoredMultilineFormatter(MultilineFormatter):
-    """Formatter that adds ANSI colors to multi-line log messages.
-
-    Args:
-        fmt: Log message format string.
-        datefmt: Date/time format string.
-        colors: Dictionary of ANSI color codes for each log level.
-        show_logger_name: Show logger name in log messages.
+    Note: Escapes curly braces in messages to prevent format string errors.
     """
+    # Escape curly braces in message to prevent format string errors
+    message = record['message'].replace('{', '{{').replace('}', '}}')
+    lines = message.split('\n')
 
-    RESET = '\033[0m'
-
-    def __init__(
-        self,
-        fmt: str | None = None,
-        datefmt: str | None = None,
-        colors: dict[str, str] | None = None,
-        show_logger_name: bool = False,
-    ):
-        super().__init__(fmt=fmt, datefmt=datefmt, show_logger_name=show_logger_name)
-        self.COLORS = (
-            colors
-            if colors is not None
-            else {
-                'DEBUG': '\033[90m',
-                'INFO': '\033[0m',
-                'WARNING': '\033[33m',
-                'ERROR': '\033[31m',
-                'CRITICAL': '\033[1m\033[31m',
-            }
-        )
+    # Format timestamp and level
+    time_str = record['time'].strftime('%Y-%m-%d %H:%M:%S.%f')[:-3]  # milliseconds
+    level_str = f'{record["level"].name: <8}'
 
-    def format(self, record):
-        lines = super().format(record).splitlines()
-        log_color = self.COLORS.get(record.levelname, self.RESET)
-        formatted_lines = [f'{log_color}{line}{self.RESET}' for line in lines]
-        return '\n'.join(formatted_lines)
-
-
-def _create_console_handler(
-    use_rich: bool = False,
-    stream: Literal['stdout', 'stderr'] = 'stdout',
-    console_width: int = 120,
-    show_path: bool = False,
-    show_logger_name: bool = False,
-    date_format: str = '%Y-%m-%d %H:%M:%S',
-    format: str = '%(message)s',
-    colors: dict[str, str] | None = None,
-) -> logging.Handler:
-    """Create a console logging handler.
+    # Single line messages - standard format
+    if len(lines) == 1:
+        result = f'<dim>{time_str}</dim> | <level>{level_str}</level> | <level>{message}</level>\n'
+        if record['exception']:
+            result += '{exception}'
+        return result
 
-    Args:
-        use_rich: If True, use RichHandler with color support.
-        stream: Output stream
-        console_width: Width of the console for Rich handler.
-        show_path: Show file paths in log messages (Rich only).
-        show_logger_name: Show logger name in log messages.
-        date_format: Date/time format string.
-        format: Log message format string.
-        colors: Dictionary of ANSI color codes for each log level.
-
-    Returns:
-        Configured logging handler (RichHandler or StreamHandler).
-    """
-    # Determine the stream object
-    stream_obj = sys.stdout if stream == 'stdout' else sys.stderr
-
-    if use_rich:
-        # Convert ANSI codes to Rich theme
-        if colors:
-            theme_dict = {}
-            for level, ansi_code in colors.items():
-                # Rich can parse ANSI codes directly!
-                try:
-                    style = Style.from_ansi(ansi_code)
-                    theme_dict[f'logging.level.{level.lower()}'] = style
-                except Exception:
-                    # Fallback to default if parsing fails
-                    pass
-
-            theme = Theme(theme_dict) if theme_dict else None
-        else:
-            theme = None
-
-        console = Console(width=console_width, theme=theme, file=stream_obj)
-        handler = RichHandler(
-            console=console,
-            rich_tracebacks=True,
-            omit_repeated_times=True,
-            show_path=show_path,
-            log_time_format=date_format,
-        )
-        handler.setFormatter(logging.Formatter(format))
-    else:
-        handler = logging.StreamHandler(stream=stream_obj)
-        handler.setFormatter(
-            ColoredMultilineFormatter(
-                fmt=format,
-                datefmt=date_format,
-                colors=colors,
-                show_logger_name=show_logger_name,
-            )
-        )
-
-    return handler
-
-
-def _create_file_handler(
-    log_file: str,
-    max_file_size: int = 10_485_760,
-    backup_count: int = 5,
-    show_logger_name: bool = False,
-    date_format: str = '%Y-%m-%d %H:%M:%S',
-    format: str = '%(message)s',
-) -> RotatingFileHandler:
-    """Create a rotating file handler to prevent huge log files.
+    # Multi-line messages - boxed format
+    indent = ' ' * len(time_str)  # Match timestamp length
 
-    Args:
-        log_file: Path to the log file.
-        max_file_size: Maximum size in bytes before rotation.
-        backup_count: Number of backup files to keep.
-        show_logger_name: Show logger name in log messages.
-        date_format: Date/time format string.
-        format: Log message format string.
-
-    Returns:
-        Configured RotatingFileHandler (without colors).
-    """
+    # Build the boxed output
+    result = f'<dim>{time_str}</dim> | <level>{level_str}</level> | <level>┌─ {lines[0]}</level>\n'
+    for line in lines[1:-1]:
+        result += f'<dim>{indent}</dim> | <level>{" " * 8}</level> | <level>│  {line}</level>\n'
+    result += f'<dim>{indent}</dim> | <level>{" " * 8}</level> | <level>└─ {lines[-1]}</level>\n'
 
-    # Ensure parent directory exists
-    log_path = Path(log_file)
-    try:
-        log_path.parent.mkdir(parents=True, exist_ok=True)
-    except PermissionError as e:
-        raise PermissionError(f"Cannot create log directory '{log_path.parent}': Permission denied") from e
+    # Add exception info if present
+    if record['exception']:
+        result += '\n{exception}'
 
-    try:
-        handler = RotatingFileHandler(
-            log_file,
-            maxBytes=max_file_size,
-            backupCount=backup_count,
-            encoding='utf-8',
-        )
-    except PermissionError as e:
-        raise PermissionError(
-            f"Cannot write to log file '{log_file}': Permission denied. "
-            f'Choose a different location or check file permissions.'
-        ) from e
-
-    handler.setFormatter(
-        MultilineFormatter(
-            fmt=format,
-            datefmt=date_format,
-            show_logger_name=show_logger_name,
-        )
-    )
-    return handler
+    return result
 
 
 def _setup_logging(
-    default_level: Literal['DEBUG', 'INFO', 'WARNING', 'ERROR', 'CRITICAL'] = 'INFO',
+    default_level: Literal['DEBUG', 'INFO', 'SUCCESS', 'WARNING', 'ERROR', 'CRITICAL'] = 'INFO',
     log_file: str | None = None,
-    use_rich_handler: bool = False,
     console: bool | Literal['stdout', 'stderr'] = False,
     max_file_size: int = 10_485_760,
     backup_count: int = 5,
-    date_format: str = '%Y-%m-%d %H:%M:%S',
-    format: str = '%(message)s',
-    console_width: int = 120,
-    show_path: bool = False,
-    show_logger_name: bool = False,
-    colors: dict[str, str] | None = None,
+    verbose_tracebacks: bool = False,
 ) -> None:
     """Internal function to setup logging - use CONFIG.apply() instead.
 
-    Configures the flixopt logger with console and/or file handlers.
-    If no handlers are configured, adds NullHandler (library best practice).
+    Configures loguru logger with console and/or file handlers.
+    Multi-line messages are automatically formatted with box-style borders.
 
     Args:
         default_level: Logging level for the logger.
         log_file: Path to log file (None to disable file logging).
-        use_rich_handler: Use Rich for enhanced console output.
-        console: Enable console logging.
-        max_file_size: Maximum log file size before rotation.
+        console: Enable console logging (True/'stdout' or 'stderr').
+        max_file_size: Maximum log file size in bytes before rotation.
         backup_count: Number of backup log files to keep.
-        date_format: Date/time format for log messages.
-        format: Log message format string.
-        console_width: Console width for Rich handler.
-        show_path: Show file paths in log messages (Rich only).
-        show_logger_name: Show logger name in log messages.
-        colors: ANSI color codes for each log level.
+        verbose_tracebacks: If True, show detailed tracebacks with variable values.
     """
-    logger = logging.getLogger('flixopt')
-    logger.setLevel(getattr(logging, default_level.upper()))
-    logger.propagate = False  # Prevent duplicate logs
-    logger.handlers.clear()
+    # Remove all existing handlers
+    logger.remove()
 
-    # Handle console parameter: False = disabled, True = stdout, 'stdout' = stdout, 'stderr' = stderr
+    # Console handler with multi-line formatting
     if console:
-        # Convert True to 'stdout', keep 'stdout'/'stderr' as-is
-        stream = 'stdout' if console is True else console
-        logger.addHandler(
-            _create_console_handler(
-                use_rich=use_rich_handler,
-                stream=stream,
-                console_width=console_width,
-                show_path=show_path,
-                show_logger_name=show_logger_name,
-                date_format=date_format,
-                format=format,
-                colors=colors,
-            )
+        stream = sys.stdout if console is True or console == 'stdout' else sys.stderr
+        logger.add(
+            stream,
+            format=_format_multiline,
+            level=default_level.upper(),
+            colorize=True,
+            backtrace=verbose_tracebacks,
+            diagnose=verbose_tracebacks,
+            enqueue=False,
         )
 
+    # File handler with rotation (plain format for files)
     if log_file:
-        logger.addHandler(
-            _create_file_handler(
-                log_file=log_file,
-                max_file_size=max_file_size,
-                backup_count=backup_count,
-                show_logger_name=show_logger_name,
-                date_format=date_format,
-                format=format,
-            )
-        )
+        log_path = Path(log_file)
+        try:
+            log_path.parent.mkdir(parents=True, exist_ok=True)
+        except PermissionError as e:
+            raise PermissionError(f"Cannot create log directory '{log_path.parent}': Permission denied") from e
 
-    # Library best practice: NullHandler if no handlers configured
-    if not logger.handlers:
-        logger.addHandler(logging.NullHandler())
+        logger.add(
+            log_file,
+            format='{time:YYYY-MM-DD HH:mm:ss.SSS} | {level: <8} | {message}',
+            level=default_level.upper(),
+            colorize=False,
+            rotation=max_file_size,
+            retention=backup_count,
+            encoding='utf-8',
+            backtrace=verbose_tracebacks,
+            diagnose=verbose_tracebacks,
+            enqueue=False,
+        )
 
 
-def change_logging_level(level_name: Literal['DEBUG', 'INFO', 'WARNING', 'ERROR', 'CRITICAL']):
-    """Change the logging level for the flixopt logger and all its handlers.
+def change_logging_level(level_name: Literal['DEBUG', 'INFO', 'SUCCESS', 'WARNING', 'ERROR', 'CRITICAL']):
+    """Change the logging level for the flixopt logger.
 
     .. deprecated:: 2.1.11
         Use ``CONFIG.Logging.level = level_name`` and ``CONFIG.apply()`` instead.
@@ -785,11 +527,8 @@ def change_logging_level(level_name: Literal['DEBUG', 'INFO', 'WARNING', 'ERROR'
         DeprecationWarning,
         stacklevel=2,
     )
-    logger = logging.getLogger('flixopt')
-    logging_level = getattr(logging, level_name.upper())
-    logger.setLevel(logging_level)
-    for handler in logger.handlers:
-        handler.setLevel(logging_level)
+    CONFIG.Logging.level = level_name.upper()
+    CONFIG.apply()
 
 
 # Initialize default config
diff --git a/flixopt/core.py b/flixopt/core.py
index 0d70e255b..7f4d2a20f 100644
--- a/flixopt/core.py
+++ b/flixopt/core.py
@@ -3,7 +3,6 @@
 It provides Datatypes, logging functionality, and some functions to transform data structures.
 """
 
-import logging
 import warnings
 from itertools import permutations
 from typing import Any, Literal, Union
@@ -11,11 +10,10 @@
 import numpy as np
 import pandas as pd
 import xarray as xr
+from loguru import logger
 
 from .types import NumericOrBool
 
-logger = logging.getLogger('flixopt')
-
 FlowSystemDimensions = Literal['time', 'period', 'scenario']
 """Possible dimensions of a FlowSystem."""
 
diff --git a/flixopt/effects.py b/flixopt/effects.py
index 02c850050..ebfc2c906 100644
--- a/flixopt/effects.py
+++ b/flixopt/effects.py
@@ -7,7 +7,6 @@
 
 from __future__ import annotations
 
-import logging
 import warnings
 from collections import deque
 from typing import TYPE_CHECKING, Literal
@@ -15,6 +14,7 @@
 import linopy
 import numpy as np
 import xarray as xr
+from loguru import logger
 
 from .features import ShareAllocationModel
 from .structure import Element, ElementContainer, ElementModel, FlowSystemModel, Submodel, register_class_for_io
@@ -25,8 +25,6 @@
     from .flow_system import FlowSystem
     from .types import Effect_PS, Effect_TPS, Numeric_PS, Numeric_TPS, Scalar
 
-logger = logging.getLogger('flixopt')
-
 
 @register_class_for_io
 class Effect(Element):
diff --git a/flixopt/elements.py b/flixopt/elements.py
index 224cc0f9c..f47002b3a 100644
--- a/flixopt/elements.py
+++ b/flixopt/elements.py
@@ -4,12 +4,12 @@
 
 from __future__ import annotations
 
-import logging
 import warnings
 from typing import TYPE_CHECKING
 
 import numpy as np
 import xarray as xr
+from loguru import logger
 
 from . import io as fx_io
 from .config import CONFIG
@@ -36,8 +36,6 @@
         Scalar,
     )
 
-logger = logging.getLogger('flixopt')
-
 
 @register_class_for_io
 class Component(Element):
@@ -532,8 +530,8 @@ def _plausibility_checks(self) -> None:
         if np.any(self.relative_minimum > 0) and self.on_off_parameters is None:
             logger.warning(
                 f'Flow {self.label_full} has a relative_minimum of {self.relative_minimum} and no on_off_parameters. '
-                f'This prevents the flow_rate from switching off (flow_rate = 0). '
-                f'Consider using on_off_parameters to allow the flow to be switched on and off.'
+                f'This prevents the Flow from switching off (flow_rate = 0). '
+                f'Consider using on_off_parameters to allow the Flow to be switched on and off.'
             )
 
         if self.previous_flow_rate is not None:
diff --git a/flixopt/features.py b/flixopt/features.py
index 519693885..fd9796ba1 100644
--- a/flixopt/features.py
+++ b/flixopt/features.py
@@ -5,7 +5,6 @@
 
 from __future__ import annotations
 
-import logging
 from typing import TYPE_CHECKING
 
 import linopy
@@ -19,8 +18,6 @@
     from .interface import InvestParameters, OnOffParameters, Piecewise
     from .types import Numeric_PS, Numeric_TPS
 
-logger = logging.getLogger('flixopt')
-
 
 class InvestmentModel(Submodel):
     """
diff --git a/flixopt/flow_system.py b/flixopt/flow_system.py
index 081359076..cf112a608 100644
--- a/flixopt/flow_system.py
+++ b/flixopt/flow_system.py
@@ -4,7 +4,6 @@
 
 from __future__ import annotations
 
-import logging
 import warnings
 from collections import defaultdict
 from itertools import chain
@@ -13,6 +12,7 @@
 import numpy as np
 import pandas as pd
 import xarray as xr
+from loguru import logger
 
 from . import io as fx_io
 from .config import CONFIG
@@ -34,8 +34,6 @@
 
     from .types import Bool_TPS, Effect_TPS, Numeric_PS, Numeric_TPS, NumericOrBool
 
-logger = logging.getLogger('flixopt')
-
 
 class FlowSystem(Interface, CompositeContainerMixin[Element]):
     """
diff --git a/flixopt/interface.py b/flixopt/interface.py
index e22ceebd5..f67f501ba 100644
--- a/flixopt/interface.py
+++ b/flixopt/interface.py
@@ -5,13 +5,13 @@
 
 from __future__ import annotations
 
-import logging
 import warnings
 from typing import TYPE_CHECKING, Any
 
 import numpy as np
 import pandas as pd
 import xarray as xr
+from loguru import logger
 
 from .config import CONFIG
 from .structure import Interface, register_class_for_io
@@ -23,9 +23,6 @@
     from .types import Effect_PS, Effect_TPS, Numeric_PS, Numeric_TPS
 
 
-logger = logging.getLogger('flixopt')
-
-
 @register_class_for_io
 class Piece(Interface):
     """Define a single linear segment with specified domain boundaries.
diff --git a/flixopt/io.py b/flixopt/io.py
index e83738d89..ffeb2474e 100644
--- a/flixopt/io.py
+++ b/flixopt/io.py
@@ -2,7 +2,6 @@
 
 import inspect
 import json
-import logging
 import os
 import pathlib
 import re
@@ -15,14 +14,13 @@
 import pandas as pd
 import xarray as xr
 import yaml
+from loguru import logger
 
 if TYPE_CHECKING:
     import linopy
 
     from .types import Numeric_TPS
 
-logger = logging.getLogger('flixopt')
-
 
 def remove_none_and_empty(obj):
     """Recursively removes None and empty dicts and lists values from a dictionary or list."""
@@ -500,7 +498,7 @@ def document_linopy_model(model: linopy.Model, path: pathlib.Path | None = None)
     }
 
     if model.status == 'warning':
-        logger.critical(f'The model has a warning status {model.status=}. Trying to extract infeasibilities')
+        logger.warning(f'The model has a warning status {model.status=}. Trying to extract infeasibilities')
         try:
             import io
             from contextlib import redirect_stdout
@@ -513,7 +511,7 @@ def document_linopy_model(model: linopy.Model, path: pathlib.Path | None = None)
 
             documentation['infeasible_constraints'] = f.getvalue()
         except NotImplementedError:
-            logger.critical(
+            logger.warning(
                 'Infeasible constraints could not get retrieved. This functionality is only availlable with gurobi'
             )
             documentation['infeasible_constraints'] = 'Not possible to retrieve infeasible constraints'
diff --git a/flixopt/modeling.py b/flixopt/modeling.py
index 13b4c0e3e..ebe739a85 100644
--- a/flixopt/modeling.py
+++ b/flixopt/modeling.py
@@ -1,14 +1,11 @@
-import logging
-
 import linopy
 import numpy as np
 import xarray as xr
+from loguru import logger
 
 from .config import CONFIG
 from .structure import Submodel
 
-logger = logging.getLogger('flixopt')
-
 
 class ModelingUtilitiesAbstract:
     """Utility functions for modeling calculations - leveraging xarray for temporal data"""
diff --git a/flixopt/network_app.py b/flixopt/network_app.py
index 2cc80e7b0..446a2e7ce 100644
--- a/flixopt/network_app.py
+++ b/flixopt/network_app.py
@@ -1,10 +1,11 @@
 from __future__ import annotations
 
-import logging
 import socket
 import threading
 from typing import TYPE_CHECKING, Any
 
+from loguru import logger
+
 try:
     import dash_cytoscape as cyto
     import dash_daq as daq
@@ -24,8 +25,6 @@
 if TYPE_CHECKING:
     from .flow_system import FlowSystem
 
-logger = logging.getLogger('flixopt')
-
 
 # Configuration class for better organization
 class VisualizationConfig:
diff --git a/flixopt/plotting.py b/flixopt/plotting.py
index 045cf7e99..27dbaf78c 100644
--- a/flixopt/plotting.py
+++ b/flixopt/plotting.py
@@ -26,7 +26,6 @@
 from __future__ import annotations
 
 import itertools
-import logging
 import os
 import pathlib
 from typing import TYPE_CHECKING, Any, Literal
@@ -40,6 +39,7 @@
 import plotly.graph_objects as go
 import plotly.offline
 import xarray as xr
+from loguru import logger
 
 from .color_processing import process_colors
 from .config import CONFIG
@@ -47,8 +47,6 @@
 if TYPE_CHECKING:
     import pyvis
 
-logger = logging.getLogger('flixopt')
-
 # Define the colors for the 'portland' colorscale in matplotlib
 _portland_colors = [
     [12 / 255, 51 / 255, 131 / 255],  # Dark blue
diff --git a/flixopt/results.py b/flixopt/results.py
index 3d9aedf62..eaff79fe4 100644
--- a/flixopt/results.py
+++ b/flixopt/results.py
@@ -2,7 +2,6 @@
 
 import copy
 import datetime
-import logging
 import pathlib
 import warnings
 from typing import TYPE_CHECKING, Any, Literal
@@ -11,6 +10,7 @@
 import numpy as np
 import pandas as pd
 import xarray as xr
+from loguru import logger
 
 from . import io as fx_io
 from . import plotting
@@ -28,9 +28,6 @@
     from .core import FlowSystemDimensions
 
 
-logger = logging.getLogger('flixopt')
-
-
 def load_mapping_from_file(path: pathlib.Path) -> dict[str, str | list[str]]:
     """Load color mapping from JSON or YAML file.
 
@@ -344,18 +341,19 @@ def flow_system(self) -> FlowSystem:
         """The restored flow_system that was used to create the calculation.
         Contains all input parameters."""
         if self._flow_system is None:
-            old_level = logger.level
-            logger.level = logging.CRITICAL
+            # Temporarily disable all logging to suppress messages during restoration
+            logger.disable('flixopt')
             try:
                 self._flow_system = FlowSystem.from_dataset(self.flow_system_data)
                 self._flow_system._connect_network()
             except Exception as e:
+                logger.enable('flixopt')  # Re-enable before logging critical message
                 logger.critical(
                     f'Not able to restore FlowSystem from dataset. Some functionality is not availlable. {e}'
                 )
                 raise _FlowSystemRestorationError(f'Not able to restore FlowSystem from dataset. {e}') from e
             finally:
-                logger.level = old_level
+                logger.enable('flixopt')
         return self._flow_system
 
     def setup_colors(
@@ -1092,7 +1090,7 @@ def to_file(
             else:
                 fx_io.document_linopy_model(self.model, path=paths.model_documentation)
 
-        logger.info(f'Saved calculation results "{name}" to {paths.model_documentation.parent}')
+        logger.success(f'Saved calculation results "{name}" to {paths.model_documentation.parent}')
 
 
 class _ElementResults:
diff --git a/flixopt/solvers.py b/flixopt/solvers.py
index e5db61192..a9a3afb46 100644
--- a/flixopt/solvers.py
+++ b/flixopt/solvers.py
@@ -4,13 +4,12 @@
 
 from __future__ import annotations
 
-import logging
 from dataclasses import dataclass, field
 from typing import Any, ClassVar
 
-from flixopt.config import CONFIG
+from loguru import logger
 
-logger = logging.getLogger('flixopt')
+from flixopt.config import CONFIG
 
 
 @dataclass
diff --git a/flixopt/structure.py b/flixopt/structure.py
index 2bce6aa52..9ddf46d31 100644
--- a/flixopt/structure.py
+++ b/flixopt/structure.py
@@ -6,11 +6,9 @@
 from __future__ import annotations
 
 import inspect
-import logging
 import re
 from dataclasses import dataclass
 from difflib import get_close_matches
-from io import StringIO
 from typing import (
     TYPE_CHECKING,
     Any,
@@ -23,8 +21,7 @@
 import numpy as np
 import pandas as pd
 import xarray as xr
-from rich.console import Console
-from rich.pretty import Pretty
+from loguru import logger
 
 from . import io as fx_io
 from .core import TimeSeriesData, get_dataarray_stats
@@ -36,8 +33,6 @@
     from .effects import EffectCollectionModel
     from .flow_system import FlowSystem
 
-logger = logging.getLogger('flixopt')
-
 
 CLASS_REGISTRY = {}
 
diff --git a/pyproject.toml b/pyproject.toml
index eb1fea0f8..4a60d7754 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -40,7 +40,7 @@ dependencies = [
     "netcdf4 >= 1.6.1, < 2",
     # Utilities
     "pyyaml >= 6.0.0, < 7",
-    "rich >= 13.0.0, < 15",
+    "loguru >= 0.7.0, < 1",
     "tqdm >= 4.66.0, < 5",
     "tomli >= 2.0.1, < 3; python_version < '3.11'", # Only needed with python 3.10 or earlier
     # Default solver
diff --git a/tests/test_config.py b/tests/test_config.py
index a78330eb4..7de58e8aa 100644
--- a/tests/test_config.py
+++ b/tests/test_config.py
@@ -1,10 +1,10 @@
 """Tests for the config module."""
 
-import logging
 import sys
 from pathlib import Path
 
 import pytest
+from loguru import logger
 
 from flixopt.config import _DEFAULTS, CONFIG, _setup_logging
 
@@ -26,7 +26,6 @@ def test_config_defaults(self):
         """Test that CONFIG has correct default values."""
         assert CONFIG.Logging.level == 'INFO'
         assert CONFIG.Logging.file is None
-        assert CONFIG.Logging.rich is False
         assert CONFIG.Logging.console is False
         assert CONFIG.Modeling.big == 10_000_000
         assert CONFIG.Modeling.epsilon == 1e-5
@@ -37,28 +36,27 @@ def test_config_defaults(self):
         assert CONFIG.Solving.log_main_results is True
         assert CONFIG.config_name == 'flixopt'
 
-    def test_module_initialization(self):
+    def test_module_initialization(self, capfd):
         """Test that logging is initialized on module import."""
         # Apply config to ensure handlers are initialized
         CONFIG.apply()
-        logger = logging.getLogger('flixopt')
-        # Should have at least one handler (file handler by default)
-        assert len(logger.handlers) == 1
-        # Should have a file handler with default settings
-        assert isinstance(logger.handlers[0], logging.NullHandler)
+        # With default config (console=False, file=None), logs should not appear
+        logger.info('test message')
+        captured = capfd.readouterr()
+        assert 'test message' not in captured.out
+        assert 'test message' not in captured.err
 
-    def test_config_apply_console(self):
+    def test_config_apply_console(self, capfd):
         """Test applying config with console logging enabled."""
         CONFIG.Logging.console = True
         CONFIG.Logging.level = 'DEBUG'
         CONFIG.apply()
 
-        logger = logging.getLogger('flixopt')
-        assert logger.level == logging.DEBUG
-        # Should have a StreamHandler for console output
-        assert any(isinstance(h, logging.StreamHandler) for h in logger.handlers)
-        # Should not have NullHandler when console is enabled
-        assert not any(isinstance(h, logging.NullHandler) for h in logger.handlers)
+        # Test that DEBUG level logs appear in console output
+        test_message = 'test debug message 12345'
+        logger.debug(test_message)
+        captured = capfd.readouterr()
+        assert test_message in captured.out or test_message in captured.err
 
     def test_config_apply_file(self, tmp_path):
         """Test applying config with file logging enabled."""
@@ -67,34 +65,42 @@ def test_config_apply_file(self, tmp_path):
         CONFIG.Logging.level = 'WARNING'
         CONFIG.apply()
 
-        logger = logging.getLogger('flixopt')
-        assert logger.level == logging.WARNING
-        # Should have a RotatingFileHandler for file output
-        from logging.handlers import RotatingFileHandler
+        # Test that WARNING level logs appear in the file
+        test_message = 'test warning message 67890'
+        logger.warning(test_message)
+        # Loguru may buffer, so we need to ensure the log is written
+        import time
 
-        assert any(isinstance(h, RotatingFileHandler) for h in logger.handlers)
+        time.sleep(0.1)  # Small delay to ensure write
+        assert log_file.exists()
+        log_content = log_file.read_text()
+        assert test_message in log_content
 
-    def test_config_apply_rich(self):
-        """Test applying config with rich logging enabled."""
-        CONFIG.Logging.console = True
-        CONFIG.Logging.rich = True
+    def test_config_apply_console_stderr(self, capfd):
+        """Test applying config with console logging to stderr."""
+        CONFIG.Logging.console = 'stderr'
+        CONFIG.Logging.level = 'INFO'
         CONFIG.apply()
 
-        logger = logging.getLogger('flixopt')
-        # Should have a RichHandler
-        from rich.logging import RichHandler
+        # Test that INFO logs appear in stderr
+        test_message = 'test info to stderr 11111'
+        logger.info(test_message)
+        captured = capfd.readouterr()
+        assert test_message in captured.err
 
-        assert any(isinstance(h, RichHandler) for h in logger.handlers)
-
-    def test_config_apply_multiple_changes(self):
+    def test_config_apply_multiple_changes(self, capfd):
         """Test applying multiple config changes at once."""
         CONFIG.Logging.console = True
         CONFIG.Logging.level = 'ERROR'
         CONFIG.apply()
 
-        logger = logging.getLogger('flixopt')
-        assert logger.level == logging.ERROR
-        assert any(isinstance(h, logging.StreamHandler) for h in logger.handlers)
+        # Test that ERROR level logs appear but lower levels don't
+        logger.warning('warning should not appear')
+        logger.error('error should appear 22222')
+        captured = capfd.readouterr()
+        output = captured.out + captured.err
+        assert 'warning should not appear' not in output
+        assert 'error should appear 22222' in output
 
     def test_config_to_dict(self):
         """Test converting CONFIG to dictionary."""
@@ -107,7 +113,6 @@ def test_config_to_dict(self):
         assert config_dict['logging']['level'] == 'DEBUG'
         assert config_dict['logging']['console'] is True
         assert config_dict['logging']['file'] is None
-        assert config_dict['logging']['rich'] is False
         assert 'modeling' in config_dict
         assert config_dict['modeling']['big'] == 10_000_000
         assert 'solving' in config_dict
@@ -172,36 +177,41 @@ def test_config_load_from_file_partial(self, tmp_path):
         # Verify console setting is preserved (not in YAML)
         assert CONFIG.Logging.console is True
 
-    def test_setup_logging_silent_default(self):
+    def test_setup_logging_silent_default(self, capfd):
         """Test that _setup_logging creates silent logger by default."""
         _setup_logging()
 
-        logger = logging.getLogger('flixopt')
-        # Should have NullHandler when console=False and log_file=None
-        assert any(isinstance(h, logging.NullHandler) for h in logger.handlers)
-        assert not logger.propagate
+        # With default settings, logs should not appear
+        logger.info('should not appear')
+        captured = capfd.readouterr()
+        assert 'should not appear' not in captured.out
+        assert 'should not appear' not in captured.err
 
-    def test_setup_logging_with_console(self):
+    def test_setup_logging_with_console(self, capfd):
         """Test _setup_logging with console output."""
         _setup_logging(console=True, default_level='DEBUG')
 
-        logger = logging.getLogger('flixopt')
-        assert logger.level == logging.DEBUG
-        assert any(isinstance(h, logging.StreamHandler) for h in logger.handlers)
+        # Test that DEBUG logs appear in console
+        test_message = 'debug console test 33333'
+        logger.debug(test_message)
+        captured = capfd.readouterr()
+        assert test_message in captured.out or test_message in captured.err
 
-    def test_setup_logging_clears_handlers(self):
+    def test_setup_logging_clears_handlers(self, capfd):
         """Test that _setup_logging clears existing handlers."""
-        logger = logging.getLogger('flixopt')
-
-        # Add a dummy handler
-        dummy_handler = logging.NullHandler()
-        logger.addHandler(dummy_handler)
-        _ = len(logger.handlers)
-
+        # Setup a handler first
         _setup_logging(console=True)
 
-        # Should have cleared old handlers and added new one
-        assert dummy_handler not in logger.handlers
+        # Call setup again with different settings - should clear and re-add
+        _setup_logging(console=True, default_level='ERROR')
+
+        # Verify new settings work: ERROR logs appear but INFO doesn't
+        logger.info('info should not appear')
+        logger.error('error should appear 44444')
+        captured = capfd.readouterr()
+        output = captured.out + captured.err
+        assert 'info should not appear' not in output
+        assert 'error should appear 44444' in output
 
     def test_change_logging_level_removed(self):
         """Test that change_logging_level function is deprecated but still exists."""
@@ -231,40 +241,43 @@ def test_public_api(self):
         # merge_configs should not exist (was removed)
         assert not hasattr(config, 'merge_configs')
 
-    def test_logging_levels(self):
+    def test_logging_levels(self, capfd):
         """Test all valid logging levels."""
-        levels = ['DEBUG', 'INFO', 'WARNING', 'ERROR', 'CRITICAL']
+        levels = ['DEBUG', 'INFO', 'SUCCESS', 'WARNING', 'ERROR', 'CRITICAL']
 
         for level in levels:
             CONFIG.Logging.level = level
             CONFIG.Logging.console = True
             CONFIG.apply()
 
-            logger = logging.getLogger('flixopt')
-            assert logger.level == getattr(logging, level)
-
-    def test_logger_propagate_disabled(self):
-        """Test that logger propagation is disabled."""
-        CONFIG.apply()
-        logger = logging.getLogger('flixopt')
-        assert not logger.propagate
+            # Test that logs at the configured level appear
+            test_message = f'test message at {level} 55555'
+            getattr(logger, level.lower())(test_message)
+            captured = capfd.readouterr()
+            output = captured.out + captured.err
+            assert test_message in output, f'Expected {level} message to appear'
 
     def test_file_handler_rotation(self, tmp_path):
-        """Test that file handler uses rotation."""
+        """Test that file handler rotation configuration is accepted."""
         log_file = tmp_path / 'rotating.log'
         CONFIG.Logging.file = str(log_file)
+        CONFIG.Logging.max_file_size = 1024
+        CONFIG.Logging.backup_count = 2
         CONFIG.apply()
 
-        logger = logging.getLogger('flixopt')
-        from logging.handlers import RotatingFileHandler
+        # Write some logs
+        for i in range(10):
+            logger.info(f'Log message {i}')
+
+        # Verify file logging works
+        import time
 
-        file_handlers = [h for h in logger.handlers if isinstance(h, RotatingFileHandler)]
-        assert len(file_handlers) == 1
+        time.sleep(0.1)
+        assert log_file.exists(), 'Log file should be created'
 
-        handler = file_handlers[0]
-        # Check rotation settings
-        assert handler.maxBytes == 10_485_760  # 10MB
-        assert handler.backupCount == 5
+        # Verify configuration values are preserved
+        assert CONFIG.Logging.max_file_size == 1024
+        assert CONFIG.Logging.backup_count == 2
 
     def test_custom_config_yaml_complete(self, tmp_path):
         """Test loading a complete custom configuration."""
@@ -274,7 +287,6 @@ def test_custom_config_yaml_complete(self, tmp_path):
 logging:
   level: CRITICAL
   console: true
-  rich: true
   file: /tmp/custom.log
 modeling:
   big: 50000000
@@ -293,7 +305,6 @@ def test_custom_config_yaml_complete(self, tmp_path):
         assert CONFIG.config_name == 'my_custom_config'
         assert CONFIG.Logging.level == 'CRITICAL'
         assert CONFIG.Logging.console is True
-        assert CONFIG.Logging.rich is True
         assert CONFIG.Logging.file == '/tmp/custom.log'
         assert CONFIG.Modeling.big == 50000000
         assert float(CONFIG.Modeling.epsilon) == 1e-4
@@ -302,9 +313,22 @@ def test_custom_config_yaml_complete(self, tmp_path):
         assert CONFIG.Solving.time_limit_seconds == 900
         assert CONFIG.Solving.log_main_results is False
 
-        # Verify logging was applied
-        logger = logging.getLogger('flixopt')
-        assert logger.level == logging.CRITICAL
+        # Verify logging was applied to both console and file
+        import time
+
+        test_message = 'critical test message 66666'
+        logger.critical(test_message)
+        time.sleep(0.1)  # Small delay to ensure write
+        # Check file exists and contains message
+        log_file_path = tmp_path / 'custom.log'
+        if not log_file_path.exists():
+            # File might be at /tmp/custom.log as specified in config
+            import os
+
+            log_file_path = os.path.expanduser('/tmp/custom.log')
+        # We can't reliably test the file at /tmp/custom.log in tests
+        # So just verify critical level messages would appear at this level
+        assert CONFIG.Logging.level == 'CRITICAL'
 
     def test_config_file_with_console_and_file(self, tmp_path):
         """Test configuration with both console and file logging enabled."""
@@ -314,21 +338,22 @@ def test_config_file_with_console_and_file(self, tmp_path):
 logging:
   level: INFO
   console: true
-  rich: false
   file: {log_file}
 """
         config_file.write_text(config_content)
 
         CONFIG.load_from_file(config_file)
 
-        logger = logging.getLogger('flixopt')
-        # Should have both StreamHandler and RotatingFileHandler
-        from logging.handlers import RotatingFileHandler
+        # Verify logging to both console and file works
+        import time
 
-        assert any(isinstance(h, logging.StreamHandler) for h in logger.handlers)
-        assert any(isinstance(h, RotatingFileHandler) for h in logger.handlers)
-        # Should NOT have NullHandler when console/file are enabled
-        assert not any(isinstance(h, logging.NullHandler) for h in logger.handlers)
+        test_message = 'info test both outputs 77777'
+        logger.info(test_message)
+        time.sleep(0.1)  # Small delay to ensure write
+        # Verify file logging works
+        assert log_file.exists()
+        log_content = log_file.read_text()
+        assert test_message in log_content
 
     def test_config_to_dict_roundtrip(self, tmp_path):
         """Test that config can be saved to dict, modified, and restored."""
@@ -416,7 +441,6 @@ def test_logger_actually_logs(self, tmp_path):
         CONFIG.Logging.level = 'DEBUG'
         CONFIG.apply()
 
-        logger = logging.getLogger('flixopt')
         test_message = 'Test log message from config test'
         logger.debug(test_message)
 
@@ -443,8 +467,7 @@ def test_config_reset(self):
         """Test that CONFIG.reset() restores all defaults."""
         # Modify all config values
         CONFIG.Logging.level = 'DEBUG'
-        CONFIG.Logging.console = False
-        CONFIG.Logging.rich = True
+        CONFIG.Logging.console = True
         CONFIG.Logging.file = '/tmp/test.log'
         CONFIG.Modeling.big = 99999999
         CONFIG.Modeling.epsilon = 1e-8
@@ -461,7 +484,6 @@ def test_config_reset(self):
         # Verify all values are back to defaults
         assert CONFIG.Logging.level == 'INFO'
         assert CONFIG.Logging.console is False
-        assert CONFIG.Logging.rich is False
         assert CONFIG.Logging.file is None
         assert CONFIG.Modeling.big == 10_000_000
         assert CONFIG.Modeling.epsilon == 1e-5
@@ -472,10 +494,23 @@ def test_config_reset(self):
         assert CONFIG.Solving.log_main_results is True
         assert CONFIG.config_name == 'flixopt'
 
-        # Verify logging was also reset
-        logger = logging.getLogger('flixopt')
-        assert logger.level == logging.INFO
-        assert isinstance(logger.handlers[0], logging.NullHandler)
+        # Verify logging was also reset (default is no logging to console/file)
+        # Test that logs don't appear with default config
+        from io import StringIO
+
+        old_stdout = sys.stdout
+        old_stderr = sys.stderr
+        sys.stdout = StringIO()
+        sys.stderr = StringIO()
+        try:
+            logger.info('should not appear after reset')
+            stdout_content = sys.stdout.getvalue()
+            stderr_content = sys.stderr.getvalue()
+            assert 'should not appear after reset' not in stdout_content
+            assert 'should not appear after reset' not in stderr_content
+        finally:
+            sys.stdout = old_stdout
+            sys.stderr = old_stderr
 
     def test_reset_matches_class_defaults(self):
         """Test that reset() values match the _DEFAULTS constants.
@@ -486,7 +521,6 @@ def test_reset_matches_class_defaults(self):
         # Modify all values to something different
         CONFIG.Logging.level = 'CRITICAL'
         CONFIG.Logging.file = '/tmp/test.log'
-        CONFIG.Logging.rich = True
         CONFIG.Logging.console = True
         CONFIG.Modeling.big = 999999
         CONFIG.Modeling.epsilon = 1e-10
@@ -509,7 +543,6 @@ def test_reset_matches_class_defaults(self):
         # Verify reset() restored exactly the _DEFAULTS values
         assert CONFIG.Logging.level == _DEFAULTS['logging']['level']
         assert CONFIG.Logging.file == _DEFAULTS['logging']['file']
-        assert CONFIG.Logging.rich == _DEFAULTS['logging']['rich']
         assert CONFIG.Logging.console == _DEFAULTS['logging']['console']
         assert CONFIG.Modeling.big == _DEFAULTS['modeling']['big']
         assert CONFIG.Modeling.epsilon == _DEFAULTS['modeling']['epsilon']

From 10efff33dbb2b6f75868c25c94b86d0e3efb842b Mon Sep 17 00:00:00 2001
From: FBumann <117816358+FBumann@users.noreply.github.com>
Date: Sat, 15 Nov 2025 23:31:52 +0100
Subject: [PATCH 08/25] Ensure flows are present

---
 flixopt/linear_converters.py | 40 ++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/flixopt/linear_converters.py b/flixopt/linear_converters.py
index 7b1b5cdbe..7fa914062 100644
--- a/flixopt/linear_converters.py
+++ b/flixopt/linear_converters.py
@@ -90,6 +90,12 @@ def __init__(
         thermal_flow = self._handle_deprecated_kwarg(kwargs, 'Q_th', 'thermal_flow', thermal_flow)
         self._validate_kwargs(kwargs)
 
+        # Validate required parameters
+        if fuel_flow is None:
+            raise ValueError(f"'{label}': fuel_flow is required and cannot be None")
+        if thermal_flow is None:
+            raise ValueError(f"'{label}': thermal_flow is required and cannot be None")
+
         super().__init__(
             label,
             inputs=[fuel_flow],
@@ -221,6 +227,12 @@ def __init__(
         thermal_flow = self._handle_deprecated_kwarg(kwargs, 'Q_th', 'thermal_flow', thermal_flow)
         self._validate_kwargs(kwargs)
 
+        # Validate required parameters
+        if power_flow is None:
+            raise ValueError(f"'{label}': power_flow is required and cannot be None")
+        if thermal_flow is None:
+            raise ValueError(f"'{label}': thermal_flow is required and cannot be None")
+
         super().__init__(
             label,
             inputs=[power_flow],
@@ -354,6 +366,12 @@ def __init__(
         cop = self._handle_deprecated_kwarg(kwargs, 'COP', 'cop', cop)
         self._validate_kwargs(kwargs)
 
+        # Validate required parameters
+        if power_flow is None:
+            raise ValueError(f"'{label}': power_flow is required and cannot be None")
+        if thermal_flow is None:
+            raise ValueError(f"'{label}': thermal_flow is required and cannot be None")
+
         super().__init__(
             label,
             inputs=[power_flow],
@@ -505,6 +523,12 @@ def __init__(
         thermal_flow = self._handle_deprecated_kwarg(kwargs, 'Q_th', 'thermal_flow', thermal_flow)
         self._validate_kwargs(kwargs)
 
+        # Validate required parameters
+        if power_flow is None:
+            raise ValueError(f"'{label}': power_flow is required and cannot be None")
+        if thermal_flow is None:
+            raise ValueError(f"'{label}': thermal_flow is required and cannot be None")
+
         super().__init__(
             label,
             inputs=[power_flow, thermal_flow],
@@ -649,6 +673,14 @@ def __init__(
         thermal_flow = self._handle_deprecated_kwarg(kwargs, 'Q_th', 'thermal_flow', thermal_flow)
         self._validate_kwargs(kwargs)
 
+        # Validate required parameters
+        if fuel_flow is None:
+            raise ValueError(f"'{label}': fuel_flow is required and cannot be None")
+        if power_flow is None:
+            raise ValueError(f"'{label}': power_flow is required and cannot be None")
+        if thermal_flow is None:
+            raise ValueError(f"'{label}': thermal_flow is required and cannot be None")
+
         super().__init__(
             label,
             inputs=[fuel_flow],
@@ -827,6 +859,14 @@ def __init__(
         cop = self._handle_deprecated_kwarg(kwargs, 'COP', 'cop', cop)
         self._validate_kwargs(kwargs)
 
+        # Validate required parameters
+        if power_flow is None:
+            raise ValueError(f"'{label}': power_flow is required and cannot be None")
+        if heat_source_flow is None:
+            raise ValueError(f"'{label}': heat_source_flow is required and cannot be None")
+        if thermal_flow is None:
+            raise ValueError(f"'{label}': thermal_flow is required and cannot be None")
+
         super().__init__(
             label,
             inputs=[power_flow, heat_source_flow],

From c7ad0e968c011ade0745575adbd3c15beb218f60 Mon Sep 17 00:00:00 2001
From: FBumann <117816358+FBumann@users.noreply.github.com>
Date: Sat, 15 Nov 2025 23:32:02 +0100
Subject: [PATCH 09/25] Improve logging

---
 flixopt/linear_converters.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/flixopt/linear_converters.py b/flixopt/linear_converters.py
index 7fa914062..343a5d277 100644
--- a/flixopt/linear_converters.py
+++ b/flixopt/linear_converters.py
@@ -997,7 +997,7 @@ def check_bounds(
 
     if not np.all(value > lower_bound):
         logger.warning(
-            "'{}.{}' <= lower bound {}. {}.min={} shape={}",
+            "'{}.{}' <= lower bound {}. {}.min={}, shape={}",
             element_label,
             parameter_label,
             lower_bound,
@@ -1007,7 +1007,7 @@ def check_bounds(
         )
     if not np.all(value < upper_bound):
         logger.warning(
-            "'{}.{}' >= upper bound {}. {}.max={} shape={}",
+            "'{}.{}' >= upper bound {}. {}.max={}, shape={}",
             element_label,
             parameter_label,
             upper_bound,

From c3bb04798200cbe7bbffd0f2aedf9b6dea69fe0f Mon Sep 17 00:00:00 2001
From: FBumann <117816358+FBumann@users.noreply.github.com>
Date: Sat, 15 Nov 2025 23:40:43 +0100
Subject: [PATCH 10/25] Remove special handling for TimeSeriesData

---
 flixopt/linear_converters.py | 11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)

diff --git a/flixopt/linear_converters.py b/flixopt/linear_converters.py
index 343a5d277..f93304973 100644
--- a/flixopt/linear_converters.py
+++ b/flixopt/linear_converters.py
@@ -886,9 +886,7 @@ def cop(self):
     @cop.setter
     def cop(self, value):
         check_bounds(value, 'cop', self.label_full, 1, 20)
-        # Unwrap TimeSeriesData before numpy comparison (consistent with check_bounds)
-        ts_value = value.data if isinstance(value, TimeSeriesData) else value
-        if np.any(np.asarray(ts_value) == 1):
+        if np.any(np.asarray(value) == 1):
             raise ValueError(f'{self.label_full}.cop must be strictly !=1 for HeatPumpWithSource.')
         self.conversion_factors = [
             {self.power_flow.label: value, self.thermal_flow.label: 1},
@@ -985,13 +983,6 @@ def check_bounds(
         lower_bound: The lower bound.
         upper_bound: The upper bound.
     """
-    if isinstance(value, TimeSeriesData):
-        value = value.data
-    if isinstance(lower_bound, TimeSeriesData):
-        lower_bound = lower_bound.data
-    if isinstance(upper_bound, TimeSeriesData):
-        upper_bound = upper_bound.data
-
     # Convert to array for shape and statistics
     value_arr = np.asarray(value)
 

From 633e977c8de1ccde6f0ee6a0a6609368a0e0b49b Mon Sep 17 00:00:00 2001
From: FBumann <117816358+FBumann@users.noreply.github.com>
Date: Sun, 16 Nov 2025 00:07:50 +0100
Subject: [PATCH 11/25] Backward Compatibility for HeatPump and
 HeatPumpWithSource  Robust Type Handling in check_bounds

---
 flixopt/linear_converters.py | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/flixopt/linear_converters.py b/flixopt/linear_converters.py
index f93304973..4a3160480 100644
--- a/flixopt/linear_converters.py
+++ b/flixopt/linear_converters.py
@@ -353,7 +353,7 @@ class HeatPump(LinearConverter):
     def __init__(
         self,
         label: str,
-        cop: Numeric_TPS,
+        cop: Numeric_TPS | None = None,
         power_flow: Flow | None = None,
         thermal_flow: Flow | None = None,
         on_off_parameters: OnOffParameters | None = None,
@@ -371,6 +371,8 @@ def __init__(
             raise ValueError(f"'{label}': power_flow is required and cannot be None")
         if thermal_flow is None:
             raise ValueError(f"'{label}': thermal_flow is required and cannot be None")
+        if cop is None:
+            raise ValueError(f"'{label}': cop is required and cannot be None")
 
         super().__init__(
             label,
@@ -844,7 +846,7 @@ class HeatPumpWithSource(LinearConverter):
     def __init__(
         self,
         label: str,
-        cop: Numeric_TPS,
+        cop: Numeric_TPS | None = None,
         power_flow: Flow | None = None,
         heat_source_flow: Flow | None = None,
         thermal_flow: Flow | None = None,
@@ -866,6 +868,8 @@ def __init__(
             raise ValueError(f"'{label}': heat_source_flow is required and cannot be None")
         if thermal_flow is None:
             raise ValueError(f"'{label}': thermal_flow is required and cannot be None")
+        if cop is None:
+            raise ValueError(f"'{label}': cop is required and cannot be None")
 
         super().__init__(
             label,
@@ -986,7 +990,7 @@ def check_bounds(
     # Convert to array for shape and statistics
     value_arr = np.asarray(value)
 
-    if not np.all(value > lower_bound):
+    if not np.all(value_arr > lower_bound):
         logger.warning(
             "'{}.{}' <= lower bound {}. {}.min={}, shape={}",
             element_label,
@@ -996,7 +1000,7 @@ def check_bounds(
             float(np.min(value_arr)),
             np.shape(value_arr),
         )
-    if not np.all(value < upper_bound):
+    if not np.all(value_arr < upper_bound):
         logger.warning(
             "'{}.{}' >= upper bound {}. {}.max={}, shape={}",
             element_label,

From a048d1bb6a14a261dd546be779d851892b903b3a Mon Sep 17 00:00:00 2001
From: FBumann <117816358+FBumann@users.noreply.github.com>
Date: Sun, 16 Nov 2025 10:27:16 +0100
Subject: [PATCH 12/25] =?UTF-8?q?Renamed=20eta=20=E2=86=92=20thermal=5Feff?=
 =?UTF-8?q?iciency=20=20Renamed=20eta=5Fth=20=E2=86=92=20thermal=5Fefficie?=
 =?UTF-8?q?ncy=20=20=20Renamed=20eta=5Fel=20=E2=86=92=20electrical=5Feffic?=
 =?UTF-8?q?iency=20=20=20=20-=20Fixed=20to=20use=20value=5Farr=20for=20com?=
 =?UTF-8?q?parisons=20instead=20of=20value?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 flixopt/linear_converters.py | 184 ++++++++++++++++++++++++++---------
 1 file changed, 140 insertions(+), 44 deletions(-)

diff --git a/flixopt/linear_converters.py b/flixopt/linear_converters.py
index 4a3160480..830b7e588 100644
--- a/flixopt/linear_converters.py
+++ b/flixopt/linear_converters.py
@@ -31,13 +31,14 @@ class Boiler(LinearConverter):
 
     Args:
         label: The label of the Element. Used to identify it in the FlowSystem.
-        eta: Thermal efficiency factor (0-1 range). Defines the ratio of thermal
+        thermal_efficiency: Thermal efficiency factor (0-1 range). Defines the ratio of thermal
             output to fuel input energy content.
         fuel_flow: Fuel input-flow representing fuel consumption.
         thermal_flow: Thermal output-flow representing heat generation.
         on_off_parameters: Parameters defining binary operation constraints and costs.
         meta_data: Used to store additional information. Not used internally but
             saved in results. Only use Python native types.
+        eta: *Deprecated*. Use `thermal_efficiency` instead.
         Q_fu: *Deprecated*. Use `fuel_flow` instead.
         Q_th: *Deprecated*. Use `thermal_flow` instead.
 
@@ -47,7 +48,7 @@ class Boiler(LinearConverter):
         ```python
         gas_boiler = Boiler(
             label='natural_gas_boiler',
-            eta=0.85,  # 85% thermal efficiency
+            thermal_efficiency=0.85,  # 85% thermal efficiency
             fuel_flow=natural_gas_flow,
             thermal_flow=hot_water_flow,
         )
@@ -58,7 +59,7 @@ class Boiler(LinearConverter):
         ```python
         biomass_boiler = Boiler(
             label='wood_chip_boiler',
-            eta=seasonal_efficiency_profile,  # Time-varying efficiency
+            thermal_efficiency=seasonal_efficiency_profile,  # Time-varying efficiency
             fuel_flow=biomass_flow,
             thermal_flow=district_heat_flow,
             on_off_parameters=OnOffParameters(
@@ -69,7 +70,7 @@ class Boiler(LinearConverter):
         ```
 
     Note:
-        The conversion relationship is: thermal_flow = fuel_flow × eta
+        The conversion relationship is: thermal_flow = fuel_flow × thermal_efficiency
 
         Efficiency should be between 0 and 1, where 1 represents perfect conversion
         (100% of fuel energy converted to useful thermal output).
@@ -78,7 +79,7 @@ class Boiler(LinearConverter):
     def __init__(
         self,
         label: str,
-        eta: Numeric_TPS,
+        thermal_efficiency: Numeric_TPS | None = None,
         fuel_flow: Flow | None = None,
         thermal_flow: Flow | None = None,
         on_off_parameters: OnOffParameters | None = None,
@@ -88,6 +89,7 @@ def __init__(
         # Handle deprecated parameters
         fuel_flow = self._handle_deprecated_kwarg(kwargs, 'Q_fu', 'fuel_flow', fuel_flow)
         thermal_flow = self._handle_deprecated_kwarg(kwargs, 'Q_th', 'thermal_flow', thermal_flow)
+        thermal_efficiency = self._handle_deprecated_kwarg(kwargs, 'eta', 'thermal_efficiency', thermal_efficiency)
         self._validate_kwargs(kwargs)
 
         # Validate required parameters
@@ -95,6 +97,8 @@ def __init__(
             raise ValueError(f"'{label}': fuel_flow is required and cannot be None")
         if thermal_flow is None:
             raise ValueError(f"'{label}': thermal_flow is required and cannot be None")
+        if thermal_efficiency is None:
+            raise ValueError(f"'{label}': thermal_efficiency is required and cannot be None")
 
         super().__init__(
             label,
@@ -105,17 +109,35 @@ def __init__(
         )
         self.fuel_flow = fuel_flow
         self.thermal_flow = thermal_flow
-        self.eta = eta  # Uses setter
+        self.thermal_efficiency = thermal_efficiency  # Uses setter
 
     @property
-    def eta(self):
+    def thermal_efficiency(self):
         return self.conversion_factors[0][self.fuel_flow.label]
 
-    @eta.setter
-    def eta(self, value):
-        check_bounds(value, 'eta', self.label_full, 0, 1)
+    @thermal_efficiency.setter
+    def thermal_efficiency(self, value):
+        check_bounds(value, 'thermal_efficiency', self.label_full, 0, 1)
         self.conversion_factors = [{self.fuel_flow.label: value, self.thermal_flow.label: 1}]
 
+    @property
+    def eta(self) -> Numeric_TPS:
+        warnings.warn(
+            'The "eta" property is deprecated. Use "thermal_efficiency" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return self.thermal_efficiency
+
+    @eta.setter
+    def eta(self, value: Numeric_TPS) -> None:
+        warnings.warn(
+            'The "eta" property is deprecated. Use "thermal_efficiency" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        self.thermal_efficiency = value
+
     @property
     def Q_fu(self) -> Flow:  # noqa: N802
         warnings.warn(
@@ -165,7 +187,7 @@ class Power2Heat(LinearConverter):
 
     Args:
         label: The label of the Element. Used to identify it in the FlowSystem.
-        eta: Thermal efficiency factor (0-1 range). For resistance heating this is
+        thermal_efficiency: Thermal efficiency factor (0-1 range). For resistance heating this is
             typically close to 1.0 (nearly 100% efficiency), but may be lower for
             electrode boilers or systems with distribution losses.
         power_flow: Electrical input-flow representing electricity consumption.
@@ -173,6 +195,7 @@ class Power2Heat(LinearConverter):
         on_off_parameters: Parameters defining binary operation constraints and costs.
         meta_data: Used to store additional information. Not used internally but
             saved in results. Only use Python native types.
+        eta: *Deprecated*. Use `thermal_efficiency` instead.
         P_el: *Deprecated*. Use `power_flow` instead.
         Q_th: *Deprecated*. Use `thermal_flow` instead.
 
@@ -182,7 +205,7 @@ class Power2Heat(LinearConverter):
         ```python
         electric_heater = Power2Heat(
             label='resistance_heater',
-            eta=0.98,  # 98% efficiency (small losses)
+            thermal_efficiency=0.98,  # 98% efficiency (small losses)
             power_flow=electricity_flow,
             thermal_flow=space_heating_flow,
         )
@@ -193,7 +216,7 @@ class Power2Heat(LinearConverter):
         ```python
         electrode_boiler = Power2Heat(
             label='electrode_steam_boiler',
-            eta=0.95,  # 95% efficiency including boiler losses
+            thermal_efficiency=0.95,  # 95% efficiency including boiler losses
             power_flow=industrial_electricity,
             thermal_flow=process_steam_flow,
             on_off_parameters=OnOffParameters(
@@ -204,9 +227,9 @@ class Power2Heat(LinearConverter):
         ```
 
     Note:
-        The conversion relationship is: thermal_flow = power_flow × eta
+        The conversion relationship is: thermal_flow = power_flow × thermal_efficiency
 
-        Unlike heat pumps, Power2Heat systems cannot exceed 100% efficiency (eta ≤ 1.0)
+        Unlike heat pumps, Power2Heat systems cannot exceed 100% efficiency (thermal_efficiency ≤ 1.0)
         as they only convert electrical energy without extracting additional energy
         from the environment. However, they provide fast response times and precise
         temperature control.
@@ -215,7 +238,7 @@ class Power2Heat(LinearConverter):
     def __init__(
         self,
         label: str,
-        eta: Numeric_TPS,
+        thermal_efficiency: Numeric_TPS | None = None,
         power_flow: Flow | None = None,
         thermal_flow: Flow | None = None,
         on_off_parameters: OnOffParameters | None = None,
@@ -225,6 +248,7 @@ def __init__(
         # Handle deprecated parameters
         power_flow = self._handle_deprecated_kwarg(kwargs, 'P_el', 'power_flow', power_flow)
         thermal_flow = self._handle_deprecated_kwarg(kwargs, 'Q_th', 'thermal_flow', thermal_flow)
+        thermal_efficiency = self._handle_deprecated_kwarg(kwargs, 'eta', 'thermal_efficiency', thermal_efficiency)
         self._validate_kwargs(kwargs)
 
         # Validate required parameters
@@ -232,6 +256,8 @@ def __init__(
             raise ValueError(f"'{label}': power_flow is required and cannot be None")
         if thermal_flow is None:
             raise ValueError(f"'{label}': thermal_flow is required and cannot be None")
+        if thermal_efficiency is None:
+            raise ValueError(f"'{label}': thermal_efficiency is required and cannot be None")
 
         super().__init__(
             label,
@@ -243,17 +269,35 @@ def __init__(
 
         self.power_flow = power_flow
         self.thermal_flow = thermal_flow
-        self.eta = eta  # Uses setter
+        self.thermal_efficiency = thermal_efficiency  # Uses setter
 
     @property
-    def eta(self):
+    def thermal_efficiency(self):
         return self.conversion_factors[0][self.power_flow.label]
 
-    @eta.setter
-    def eta(self, value):
-        check_bounds(value, 'eta', self.label_full, 0, 1)
+    @thermal_efficiency.setter
+    def thermal_efficiency(self, value):
+        check_bounds(value, 'thermal_efficiency', self.label_full, 0, 1)
         self.conversion_factors = [{self.power_flow.label: value, self.thermal_flow.label: 1}]
 
+    @property
+    def eta(self) -> Numeric_TPS:
+        warnings.warn(
+            'The "eta" property is deprecated. Use "thermal_efficiency" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return self.thermal_efficiency
+
+    @eta.setter
+    def eta(self, value: Numeric_TPS) -> None:
+        warnings.warn(
+            'The "eta" property is deprecated. Use "thermal_efficiency" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        self.thermal_efficiency = value
+
     @property
     def P_el(self) -> Flow:  # noqa: N802
         warnings.warn(
@@ -601,9 +645,9 @@ class CHP(LinearConverter):
 
     Args:
         label: The label of the Element. Used to identify it in the FlowSystem.
-        eta_th: Thermal efficiency factor (0-1 range). Defines the fraction of fuel
+        thermal_efficiency: Thermal efficiency factor (0-1 range). Defines the fraction of fuel
             energy converted to useful thermal output.
-        eta_el: Electrical efficiency factor (0-1 range). Defines the fraction of fuel
+        electrical_efficiency: Electrical efficiency factor (0-1 range). Defines the fraction of fuel
             energy converted to electrical output.
         fuel_flow: Fuel input-flow representing fuel consumption.
         power_flow: Electrical output-flow representing electricity generation.
@@ -611,6 +655,8 @@ class CHP(LinearConverter):
         on_off_parameters: Parameters defining binary operation constraints and costs.
         meta_data: Used to store additional information. Not used internally but
             saved in results. Only use Python native types.
+        eta_th: *Deprecated*. Use `thermal_efficiency` instead.
+        eta_el: *Deprecated*. Use `electrical_efficiency` instead.
         Q_fu: *Deprecated*. Use `fuel_flow` instead.
         P_el: *Deprecated*. Use `power_flow` instead.
         Q_th: *Deprecated*. Use `thermal_flow` instead.
@@ -621,8 +667,8 @@ class CHP(LinearConverter):
         ```python
         gas_chp = CHP(
             label='natural_gas_chp',
-            eta_th=0.45,  # 45% thermal efficiency
-            eta_el=0.35,  # 35% electrical efficiency (80% total)
+            thermal_efficiency=0.45,  # 45% thermal efficiency
+            electrical_efficiency=0.35,  # 35% electrical efficiency (80% total)
             fuel_flow=natural_gas_flow,
             power_flow=electricity_flow,
             thermal_flow=district_heat_flow,
@@ -634,8 +680,8 @@ class CHP(LinearConverter):
         ```python
         industrial_chp = CHP(
             label='industrial_chp',
-            eta_th=0.40,
-            eta_el=0.38,
+            thermal_efficiency=0.40,
+            electrical_efficiency=0.38,
             fuel_flow=fuel_gas_flow,
             power_flow=plant_electricity,
             thermal_flow=process_steam,
@@ -649,10 +695,10 @@ class CHP(LinearConverter):
 
     Note:
         The conversion relationships are:
-        - thermal_flow = fuel_flow × eta_th (thermal output)
-        - power_flow = fuel_flow × eta_el (electrical output)
+        - thermal_flow = fuel_flow × thermal_efficiency (thermal output)
+        - power_flow = fuel_flow × electrical_efficiency (electrical output)
 
-        Total efficiency (eta_th + eta_el) should be ≤ 1.0, with typical combined
+        Total efficiency (thermal_efficiency + electrical_efficiency) should be ≤ 1.0, with typical combined
         efficiencies of 80-90% for modern CHP units. This provides significant
         efficiency gains compared to separate heat and power generation.
     """
@@ -660,8 +706,8 @@ class CHP(LinearConverter):
     def __init__(
         self,
         label: str,
-        eta_th: Numeric_TPS,
-        eta_el: Numeric_TPS,
+        thermal_efficiency: Numeric_TPS | None = None,
+        electrical_efficiency: Numeric_TPS | None = None,
         fuel_flow: Flow | None = None,
         power_flow: Flow | None = None,
         thermal_flow: Flow | None = None,
@@ -673,6 +719,10 @@ def __init__(
         fuel_flow = self._handle_deprecated_kwarg(kwargs, 'Q_fu', 'fuel_flow', fuel_flow)
         power_flow = self._handle_deprecated_kwarg(kwargs, 'P_el', 'power_flow', power_flow)
         thermal_flow = self._handle_deprecated_kwarg(kwargs, 'Q_th', 'thermal_flow', thermal_flow)
+        thermal_efficiency = self._handle_deprecated_kwarg(kwargs, 'eta_th', 'thermal_efficiency', thermal_efficiency)
+        electrical_efficiency = self._handle_deprecated_kwarg(
+            kwargs, 'eta_el', 'electrical_efficiency', electrical_efficiency
+        )
         self._validate_kwargs(kwargs)
 
         # Validate required parameters
@@ -682,6 +732,10 @@ def __init__(
             raise ValueError(f"'{label}': power_flow is required and cannot be None")
         if thermal_flow is None:
             raise ValueError(f"'{label}': thermal_flow is required and cannot be None")
+        if thermal_efficiency is None:
+            raise ValueError(f"'{label}': thermal_efficiency is required and cannot be None")
+        if electrical_efficiency is None:
+            raise ValueError(f"'{label}': electrical_efficiency is required and cannot be None")
 
         super().__init__(
             label,
@@ -695,29 +749,71 @@ def __init__(
         self.fuel_flow = fuel_flow
         self.power_flow = power_flow
         self.thermal_flow = thermal_flow
-        self.eta_th = eta_th  # Uses setter
-        self.eta_el = eta_el  # Uses setter
-
-        check_bounds(eta_el + eta_th, 'eta_th+eta_el', self.label_full, 0, 1)
+        self.thermal_efficiency = thermal_efficiency  # Uses setter
+        self.electrical_efficiency = electrical_efficiency  # Uses setter
+
+        check_bounds(
+            electrical_efficiency + thermal_efficiency,
+            'thermal_efficiency+electrical_efficiency',
+            self.label_full,
+            0,
+            1,
+        )
 
     @property
-    def eta_th(self):
+    def thermal_efficiency(self):
         return self.conversion_factors[0][self.fuel_flow.label]
 
-    @eta_th.setter
-    def eta_th(self, value):
-        check_bounds(value, 'eta_th', self.label_full, 0, 1)
+    @thermal_efficiency.setter
+    def thermal_efficiency(self, value):
+        check_bounds(value, 'thermal_efficiency', self.label_full, 0, 1)
         self.conversion_factors[0] = {self.fuel_flow.label: value, self.thermal_flow.label: 1}
 
     @property
-    def eta_el(self):
+    def electrical_efficiency(self):
         return self.conversion_factors[1][self.fuel_flow.label]
 
-    @eta_el.setter
-    def eta_el(self, value):
-        check_bounds(value, 'eta_el', self.label_full, 0, 1)
+    @electrical_efficiency.setter
+    def electrical_efficiency(self, value):
+        check_bounds(value, 'electrical_efficiency', self.label_full, 0, 1)
         self.conversion_factors[1] = {self.fuel_flow.label: value, self.power_flow.label: 1}
 
+    @property
+    def eta_th(self) -> Numeric_TPS:
+        warnings.warn(
+            'The "eta_th" property is deprecated. Use "thermal_efficiency" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return self.thermal_efficiency
+
+    @eta_th.setter
+    def eta_th(self, value: Numeric_TPS) -> None:
+        warnings.warn(
+            'The "eta_th" property is deprecated. Use "thermal_efficiency" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        self.thermal_efficiency = value
+
+    @property
+    def eta_el(self) -> Numeric_TPS:
+        warnings.warn(
+            'The "eta_el" property is deprecated. Use "electrical_efficiency" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return self.electrical_efficiency
+
+    @eta_el.setter
+    def eta_el(self, value: Numeric_TPS) -> None:
+        warnings.warn(
+            'The "eta_el" property is deprecated. Use "electrical_efficiency" instead.',
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        self.electrical_efficiency = value
+
     @property
     def Q_fu(self) -> Flow:  # noqa: N802
         warnings.warn(

From 1c57f8356f78b07956c5460c9996d4999bef09d0 Mon Sep 17 00:00:00 2001
From: FBumann <117816358+FBumann@users.noreply.github.com>
Date: Sun, 16 Nov 2025 10:28:21 +0100
Subject: [PATCH 13/25] Rename power_flow to electrical_flow

---
 CHANGELOG.md                 |  10 +--
 flixopt/linear_converters.py | 168 +++++++++++++++++------------------
 2 files changed, 89 insertions(+), 89 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 833ddd3c0..7683da796 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -77,11 +77,11 @@ If upgrading from v2.x, see the [v3.0.0 release notes](https://github.com/flixOp
 - **Type handling improvements**: Updated internal data handling to work seamlessly with the new type system
 - **Parameter renaming in `linear_converters.py`**: Renamed parameters to use lowercase, descriptive names for better consistency:
     - `Boiler`: `Q_fu` → `fuel_flow`, `Q_th` → `thermal_flow`
-    - `Power2Heat`: `P_el` → `power_flow`, `Q_th` → `thermal_flow`
-    - `HeatPump`: `COP` → `cop`, `P_el` → `power_flow`, `Q_th` → `thermal_flow`
-    - `CoolingTower`: `P_el` → `power_flow`, `Q_th` → `thermal_flow`
-    - `CHP`: `Q_fu` → `fuel_flow`, `P_el` → `power_flow`, `Q_th` → `thermal_flow`
-    - `HeatPumpWithSource`: `COP` → `cop`, `P_el` → `power_flow`, `Q_ab` → `heat_source_flow`, `Q_th` → `thermal_flow`
+    - `Power2Heat`: `P_el` → `electrical_flow`, `Q_th` → `thermal_flow`
+    - `HeatPump`: `COP` → `cop`, `P_el` → `electrical_flow`, `Q_th` → `thermal_flow`
+    - `CoolingTower`: `P_el` → `electrical_flow`, `Q_th` → `thermal_flow`
+    - `CHP`: `Q_fu` → `fuel_flow`, `P_el` → `electrical_flow`, `Q_th` → `thermal_flow`
+    - `HeatPumpWithSource`: `COP` → `cop`, `P_el` → `electrical_flow`, `Q_ab` → `heat_source_flow`, `Q_th` → `thermal_flow`
 
 ### 🗑️ Deprecated
 - **Old parameter names in `linear_converters.py`**: The old uppercase parameter names are now deprecated and accessible as properties that emit `DeprecationWarning`. They will be removed in v4.0.0:
diff --git a/flixopt/linear_converters.py b/flixopt/linear_converters.py
index 830b7e588..055425eae 100644
--- a/flixopt/linear_converters.py
+++ b/flixopt/linear_converters.py
@@ -190,13 +190,13 @@ class Power2Heat(LinearConverter):
         thermal_efficiency: Thermal efficiency factor (0-1 range). For resistance heating this is
             typically close to 1.0 (nearly 100% efficiency), but may be lower for
             electrode boilers or systems with distribution losses.
-        power_flow: Electrical input-flow representing electricity consumption.
+        electrical_flow: Electrical input-flow representing electricity consumption.
         thermal_flow: Thermal output-flow representing heat generation.
         on_off_parameters: Parameters defining binary operation constraints and costs.
         meta_data: Used to store additional information. Not used internally but
             saved in results. Only use Python native types.
         eta: *Deprecated*. Use `thermal_efficiency` instead.
-        P_el: *Deprecated*. Use `power_flow` instead.
+        P_el: *Deprecated*. Use `electrical_flow` instead.
         Q_th: *Deprecated*. Use `thermal_flow` instead.
 
     Examples:
@@ -206,7 +206,7 @@ class Power2Heat(LinearConverter):
         electric_heater = Power2Heat(
             label='resistance_heater',
             thermal_efficiency=0.98,  # 98% efficiency (small losses)
-            power_flow=electricity_flow,
+            electrical_flow=electricity_flow,
             thermal_flow=space_heating_flow,
         )
         ```
@@ -217,7 +217,7 @@ class Power2Heat(LinearConverter):
         electrode_boiler = Power2Heat(
             label='electrode_steam_boiler',
             thermal_efficiency=0.95,  # 95% efficiency including boiler losses
-            power_flow=industrial_electricity,
+            electrical_flow=industrial_electricity,
             thermal_flow=process_steam_flow,
             on_off_parameters=OnOffParameters(
                 consecutive_on_hours_min=1,  # Minimum 1-hour operation
@@ -227,7 +227,7 @@ class Power2Heat(LinearConverter):
         ```
 
     Note:
-        The conversion relationship is: thermal_flow = power_flow × thermal_efficiency
+        The conversion relationship is: thermal_flow = electrical_flow × thermal_efficiency
 
         Unlike heat pumps, Power2Heat systems cannot exceed 100% efficiency (thermal_efficiency ≤ 1.0)
         as they only convert electrical energy without extracting additional energy
@@ -239,21 +239,21 @@ def __init__(
         self,
         label: str,
         thermal_efficiency: Numeric_TPS | None = None,
-        power_flow: Flow | None = None,
+        electrical_flow: Flow | None = None,
         thermal_flow: Flow | None = None,
         on_off_parameters: OnOffParameters | None = None,
         meta_data: dict | None = None,
         **kwargs,
     ):
         # Handle deprecated parameters
-        power_flow = self._handle_deprecated_kwarg(kwargs, 'P_el', 'power_flow', power_flow)
+        electrical_flow = self._handle_deprecated_kwarg(kwargs, 'P_el', 'electrical_flow', electrical_flow)
         thermal_flow = self._handle_deprecated_kwarg(kwargs, 'Q_th', 'thermal_flow', thermal_flow)
         thermal_efficiency = self._handle_deprecated_kwarg(kwargs, 'eta', 'thermal_efficiency', thermal_efficiency)
         self._validate_kwargs(kwargs)
 
         # Validate required parameters
-        if power_flow is None:
-            raise ValueError(f"'{label}': power_flow is required and cannot be None")
+        if electrical_flow is None:
+            raise ValueError(f"'{label}': electrical_flow is required and cannot be None")
         if thermal_flow is None:
             raise ValueError(f"'{label}': thermal_flow is required and cannot be None")
         if thermal_efficiency is None:
@@ -261,24 +261,24 @@ def __init__(
 
         super().__init__(
             label,
-            inputs=[power_flow],
+            inputs=[electrical_flow],
             outputs=[thermal_flow],
             on_off_parameters=on_off_parameters,
             meta_data=meta_data,
         )
 
-        self.power_flow = power_flow
+        self.electrical_flow = electrical_flow
         self.thermal_flow = thermal_flow
         self.thermal_efficiency = thermal_efficiency  # Uses setter
 
     @property
     def thermal_efficiency(self):
-        return self.conversion_factors[0][self.power_flow.label]
+        return self.conversion_factors[0][self.electrical_flow.label]
 
     @thermal_efficiency.setter
     def thermal_efficiency(self, value):
         check_bounds(value, 'thermal_efficiency', self.label_full, 0, 1)
-        self.conversion_factors = [{self.power_flow.label: value, self.thermal_flow.label: 1}]
+        self.conversion_factors = [{self.electrical_flow.label: value, self.thermal_flow.label: 1}]
 
     @property
     def eta(self) -> Numeric_TPS:
@@ -301,20 +301,20 @@ def eta(self, value: Numeric_TPS) -> None:
     @property
     def P_el(self) -> Flow:  # noqa: N802
         warnings.warn(
-            'The "P_el" property is deprecated. Use "power_flow" instead.',
+            'The "P_el" property is deprecated. Use "electrical_flow" instead.',
             DeprecationWarning,
             stacklevel=2,
         )
-        return self.power_flow
+        return self.electrical_flow
 
     @P_el.setter
     def P_el(self, value: Flow) -> None:  # noqa: N802
         warnings.warn(
-            'The "P_el" property is deprecated. Use "power_flow" instead.',
+            'The "P_el" property is deprecated. Use "electrical_flow" instead.',
             DeprecationWarning,
             stacklevel=2,
         )
-        self.power_flow = value
+        self.electrical_flow = value
 
     @property
     def Q_th(self) -> Flow:  # noqa: N802
@@ -350,13 +350,13 @@ class HeatPump(LinearConverter):
         cop: Coefficient of Performance (typically 1-20 range). Defines the ratio of
             thermal output to electrical input. COP > 1 indicates the heat pump extracts
             additional energy from the environment.
-        power_flow: Electrical input-flow representing electricity consumption.
+        electrical_flow: Electrical input-flow representing electricity consumption.
         thermal_flow: Thermal output-flow representing heat generation.
         on_off_parameters: Parameters defining binary operation constraints and costs.
         meta_data: Used to store additional information. Not used internally but
             saved in results. Only use Python native types.
         COP: *Deprecated*. Use `cop` instead.
-        P_el: *Deprecated*. Use `power_flow` instead.
+        P_el: *Deprecated*. Use `electrical_flow` instead.
         Q_th: *Deprecated*. Use `thermal_flow` instead.
 
     Examples:
@@ -366,7 +366,7 @@ class HeatPump(LinearConverter):
         air_hp = HeatPump(
             label='air_source_heat_pump',
             cop=3.5,  # COP of 3.5 (350% efficiency)
-            power_flow=electricity_flow,
+            electrical_flow=electricity_flow,
             thermal_flow=heating_flow,
         )
         ```
@@ -377,7 +377,7 @@ class HeatPump(LinearConverter):
         ground_hp = HeatPump(
             label='geothermal_heat_pump',
             cop=temperature_dependent_cop,  # Time-varying COP based on ground temp
-            power_flow=electricity_flow,
+            electrical_flow=electricity_flow,
             thermal_flow=radiant_heating_flow,
             on_off_parameters=OnOffParameters(
                 consecutive_on_hours_min=2,  # Avoid frequent cycling
@@ -387,7 +387,7 @@ class HeatPump(LinearConverter):
         ```
 
     Note:
-        The conversion relationship is: thermal_flow = power_flow × COP
+        The conversion relationship is: thermal_flow = electrical_flow × COP
 
         COP should be greater than 1 for realistic heat pump operation, with typical
         values ranging from 2-6 depending on technology and operating conditions.
@@ -398,21 +398,21 @@ def __init__(
         self,
         label: str,
         cop: Numeric_TPS | None = None,
-        power_flow: Flow | None = None,
+        electrical_flow: Flow | None = None,
         thermal_flow: Flow | None = None,
         on_off_parameters: OnOffParameters | None = None,
         meta_data: dict | None = None,
         **kwargs,
     ):
         # Handle deprecated parameters
-        power_flow = self._handle_deprecated_kwarg(kwargs, 'P_el', 'power_flow', power_flow)
+        electrical_flow = self._handle_deprecated_kwarg(kwargs, 'P_el', 'electrical_flow', electrical_flow)
         thermal_flow = self._handle_deprecated_kwarg(kwargs, 'Q_th', 'thermal_flow', thermal_flow)
         cop = self._handle_deprecated_kwarg(kwargs, 'COP', 'cop', cop)
         self._validate_kwargs(kwargs)
 
         # Validate required parameters
-        if power_flow is None:
-            raise ValueError(f"'{label}': power_flow is required and cannot be None")
+        if electrical_flow is None:
+            raise ValueError(f"'{label}': electrical_flow is required and cannot be None")
         if thermal_flow is None:
             raise ValueError(f"'{label}': thermal_flow is required and cannot be None")
         if cop is None:
@@ -420,24 +420,24 @@ def __init__(
 
         super().__init__(
             label,
-            inputs=[power_flow],
+            inputs=[electrical_flow],
             outputs=[thermal_flow],
             conversion_factors=[],
             on_off_parameters=on_off_parameters,
             meta_data=meta_data,
         )
-        self.power_flow = power_flow
+        self.electrical_flow = electrical_flow
         self.thermal_flow = thermal_flow
         self.cop = cop  # Uses setter
 
     @property
     def cop(self):
-        return self.conversion_factors[0][self.power_flow.label]
+        return self.conversion_factors[0][self.electrical_flow.label]
 
     @cop.setter
     def cop(self, value):
         check_bounds(value, 'cop', self.label_full, 1, 20)
-        self.conversion_factors = [{self.power_flow.label: value, self.thermal_flow.label: 1}]
+        self.conversion_factors = [{self.electrical_flow.label: value, self.thermal_flow.label: 1}]
 
     @property
     def COP(self) -> Numeric_TPS:  # noqa: N802
@@ -460,20 +460,20 @@ def COP(self, value: Numeric_TPS) -> None:  # noqa: N802
     @property
     def P_el(self) -> Flow:  # noqa: N802
         warnings.warn(
-            'The "P_el" property is deprecated. Use "power_flow" instead.',
+            'The "P_el" property is deprecated. Use "electrical_flow" instead.',
             DeprecationWarning,
             stacklevel=2,
         )
-        return self.power_flow
+        return self.electrical_flow
 
     @P_el.setter
     def P_el(self, value: Flow) -> None:  # noqa: N802
         warnings.warn(
-            'The "P_el" property is deprecated. Use "power_flow" instead.',
+            'The "P_el" property is deprecated. Use "electrical_flow" instead.',
             DeprecationWarning,
             stacklevel=2,
         )
-        self.power_flow = value
+        self.electrical_flow = value
 
     @property
     def Q_th(self) -> Flow:  # noqa: N802
@@ -509,12 +509,12 @@ class CoolingTower(LinearConverter):
         specific_electricity_demand: Auxiliary electricity demand per unit of cooling
             power (dimensionless, typically 0.01-0.05 range). Represents the fraction
             of thermal power that must be supplied as electricity for fans and pumps.
-        power_flow: Electrical input-flow representing electricity consumption for fans/pumps.
+        electrical_flow: Electrical input-flow representing electricity consumption for fans/pumps.
         thermal_flow: Thermal input-flow representing waste heat to be rejected to environment.
         on_off_parameters: Parameters defining binary operation constraints and costs.
         meta_data: Used to store additional information. Not used internally but
             saved in results. Only use Python native types.
-        P_el: *Deprecated*. Use `power_flow` instead.
+        P_el: *Deprecated*. Use `electrical_flow` instead.
         Q_th: *Deprecated*. Use `thermal_flow` instead.
 
     Examples:
@@ -524,7 +524,7 @@ class CoolingTower(LinearConverter):
         cooling_tower = CoolingTower(
             label='process_cooling_tower',
             specific_electricity_demand=0.025,  # 2.5% auxiliary power
-            power_flow=cooling_electricity,
+            electrical_flow=cooling_electricity,
             thermal_flow=waste_heat_flow,
         )
         ```
@@ -535,7 +535,7 @@ class CoolingTower(LinearConverter):
         condenser_cooling = CoolingTower(
             label='power_plant_cooling',
             specific_electricity_demand=0.015,  # 1.5% auxiliary power
-            power_flow=auxiliary_electricity,
+            electrical_flow=auxiliary_electricity,
             thermal_flow=condenser_waste_heat,
             on_off_parameters=OnOffParameters(
                 consecutive_on_hours_min=4,  # Minimum operation time
@@ -545,7 +545,7 @@ class CoolingTower(LinearConverter):
         ```
 
     Note:
-        The conversion relationship is: power_flow = thermal_flow × specific_electricity_demand
+        The conversion relationship is: electrical_flow = thermal_flow × specific_electricity_demand
 
         The cooling tower consumes electrical power proportional to the thermal load.
         No thermal energy is produced - all thermal input is rejected to the environment.
@@ -558,32 +558,32 @@ def __init__(
         self,
         label: str,
         specific_electricity_demand: Numeric_TPS,
-        power_flow: Flow | None = None,
+        electrical_flow: Flow | None = None,
         thermal_flow: Flow | None = None,
         on_off_parameters: OnOffParameters | None = None,
         meta_data: dict | None = None,
         **kwargs,
     ):
         # Handle deprecated parameters
-        power_flow = self._handle_deprecated_kwarg(kwargs, 'P_el', 'power_flow', power_flow)
+        electrical_flow = self._handle_deprecated_kwarg(kwargs, 'P_el', 'electrical_flow', electrical_flow)
         thermal_flow = self._handle_deprecated_kwarg(kwargs, 'Q_th', 'thermal_flow', thermal_flow)
         self._validate_kwargs(kwargs)
 
         # Validate required parameters
-        if power_flow is None:
-            raise ValueError(f"'{label}': power_flow is required and cannot be None")
+        if electrical_flow is None:
+            raise ValueError(f"'{label}': electrical_flow is required and cannot be None")
         if thermal_flow is None:
             raise ValueError(f"'{label}': thermal_flow is required and cannot be None")
 
         super().__init__(
             label,
-            inputs=[power_flow, thermal_flow],
+            inputs=[electrical_flow, thermal_flow],
             outputs=[],
             on_off_parameters=on_off_parameters,
             meta_data=meta_data,
         )
 
-        self.power_flow = power_flow
+        self.electrical_flow = electrical_flow
         self.thermal_flow = thermal_flow
         self.specific_electricity_demand = specific_electricity_demand  # Uses setter
 
@@ -594,25 +594,25 @@ def specific_electricity_demand(self):
     @specific_electricity_demand.setter
     def specific_electricity_demand(self, value):
         check_bounds(value, 'specific_electricity_demand', self.label_full, 0, 1)
-        self.conversion_factors = [{self.power_flow.label: -1, self.thermal_flow.label: value}]
+        self.conversion_factors = [{self.electrical_flow.label: -1, self.thermal_flow.label: value}]
 
     @property
     def P_el(self) -> Flow:  # noqa: N802
         warnings.warn(
-            'The "P_el" property is deprecated. Use "power_flow" instead.',
+            'The "P_el" property is deprecated. Use "electrical_flow" instead.',
             DeprecationWarning,
             stacklevel=2,
         )
-        return self.power_flow
+        return self.electrical_flow
 
     @P_el.setter
     def P_el(self, value: Flow) -> None:  # noqa: N802
         warnings.warn(
-            'The "P_el" property is deprecated. Use "power_flow" instead.',
+            'The "P_el" property is deprecated. Use "electrical_flow" instead.',
             DeprecationWarning,
             stacklevel=2,
         )
-        self.power_flow = value
+        self.electrical_flow = value
 
     @property
     def Q_th(self) -> Flow:  # noqa: N802
@@ -650,7 +650,7 @@ class CHP(LinearConverter):
         electrical_efficiency: Electrical efficiency factor (0-1 range). Defines the fraction of fuel
             energy converted to electrical output.
         fuel_flow: Fuel input-flow representing fuel consumption.
-        power_flow: Electrical output-flow representing electricity generation.
+        electrical_flow: Electrical output-flow representing electricity generation.
         thermal_flow: Thermal output-flow representing heat generation.
         on_off_parameters: Parameters defining binary operation constraints and costs.
         meta_data: Used to store additional information. Not used internally but
@@ -658,7 +658,7 @@ class CHP(LinearConverter):
         eta_th: *Deprecated*. Use `thermal_efficiency` instead.
         eta_el: *Deprecated*. Use `electrical_efficiency` instead.
         Q_fu: *Deprecated*. Use `fuel_flow` instead.
-        P_el: *Deprecated*. Use `power_flow` instead.
+        P_el: *Deprecated*. Use `electrical_flow` instead.
         Q_th: *Deprecated*. Use `thermal_flow` instead.
 
     Examples:
@@ -670,7 +670,7 @@ class CHP(LinearConverter):
             thermal_efficiency=0.45,  # 45% thermal efficiency
             electrical_efficiency=0.35,  # 35% electrical efficiency (80% total)
             fuel_flow=natural_gas_flow,
-            power_flow=electricity_flow,
+            electrical_flow=electricity_flow,
             thermal_flow=district_heat_flow,
         )
         ```
@@ -683,7 +683,7 @@ class CHP(LinearConverter):
             thermal_efficiency=0.40,
             electrical_efficiency=0.38,
             fuel_flow=fuel_gas_flow,
-            power_flow=plant_electricity,
+            electrical_flow=plant_electricity,
             thermal_flow=process_steam,
             on_off_parameters=OnOffParameters(
                 consecutive_on_hours_min=8,  # Minimum 8-hour operation
@@ -696,7 +696,7 @@ class CHP(LinearConverter):
     Note:
         The conversion relationships are:
         - thermal_flow = fuel_flow × thermal_efficiency (thermal output)
-        - power_flow = fuel_flow × electrical_efficiency (electrical output)
+        - electrical_flow = fuel_flow × electrical_efficiency (electrical output)
 
         Total efficiency (thermal_efficiency + electrical_efficiency) should be ≤ 1.0, with typical combined
         efficiencies of 80-90% for modern CHP units. This provides significant
@@ -709,7 +709,7 @@ def __init__(
         thermal_efficiency: Numeric_TPS | None = None,
         electrical_efficiency: Numeric_TPS | None = None,
         fuel_flow: Flow | None = None,
-        power_flow: Flow | None = None,
+        electrical_flow: Flow | None = None,
         thermal_flow: Flow | None = None,
         on_off_parameters: OnOffParameters | None = None,
         meta_data: dict | None = None,
@@ -717,7 +717,7 @@ def __init__(
     ):
         # Handle deprecated parameters
         fuel_flow = self._handle_deprecated_kwarg(kwargs, 'Q_fu', 'fuel_flow', fuel_flow)
-        power_flow = self._handle_deprecated_kwarg(kwargs, 'P_el', 'power_flow', power_flow)
+        electrical_flow = self._handle_deprecated_kwarg(kwargs, 'P_el', 'electrical_flow', electrical_flow)
         thermal_flow = self._handle_deprecated_kwarg(kwargs, 'Q_th', 'thermal_flow', thermal_flow)
         thermal_efficiency = self._handle_deprecated_kwarg(kwargs, 'eta_th', 'thermal_efficiency', thermal_efficiency)
         electrical_efficiency = self._handle_deprecated_kwarg(
@@ -728,8 +728,8 @@ def __init__(
         # Validate required parameters
         if fuel_flow is None:
             raise ValueError(f"'{label}': fuel_flow is required and cannot be None")
-        if power_flow is None:
-            raise ValueError(f"'{label}': power_flow is required and cannot be None")
+        if electrical_flow is None:
+            raise ValueError(f"'{label}': electrical_flow is required and cannot be None")
         if thermal_flow is None:
             raise ValueError(f"'{label}': thermal_flow is required and cannot be None")
         if thermal_efficiency is None:
@@ -740,14 +740,14 @@ def __init__(
         super().__init__(
             label,
             inputs=[fuel_flow],
-            outputs=[thermal_flow, power_flow],
+            outputs=[thermal_flow, electrical_flow],
             conversion_factors=[{}, {}],
             on_off_parameters=on_off_parameters,
             meta_data=meta_data,
         )
 
         self.fuel_flow = fuel_flow
-        self.power_flow = power_flow
+        self.electrical_flow = electrical_flow
         self.thermal_flow = thermal_flow
         self.thermal_efficiency = thermal_efficiency  # Uses setter
         self.electrical_efficiency = electrical_efficiency  # Uses setter
@@ -776,7 +776,7 @@ def electrical_efficiency(self):
     @electrical_efficiency.setter
     def electrical_efficiency(self, value):
         check_bounds(value, 'electrical_efficiency', self.label_full, 0, 1)
-        self.conversion_factors[1] = {self.fuel_flow.label: value, self.power_flow.label: 1}
+        self.conversion_factors[1] = {self.fuel_flow.label: value, self.electrical_flow.label: 1}
 
     @property
     def eta_th(self) -> Numeric_TPS:
@@ -835,20 +835,20 @@ def Q_fu(self, value: Flow) -> None:  # noqa: N802
     @property
     def P_el(self) -> Flow:  # noqa: N802
         warnings.warn(
-            'The "P_el" property is deprecated. Use "power_flow" instead.',
+            'The "P_el" property is deprecated. Use "electrical_flow" instead.',
             DeprecationWarning,
             stacklevel=2,
         )
-        return self.power_flow
+        return self.electrical_flow
 
     @P_el.setter
     def P_el(self, value: Flow) -> None:  # noqa: N802
         warnings.warn(
-            'The "P_el" property is deprecated. Use "power_flow" instead.',
+            'The "P_el" property is deprecated. Use "electrical_flow" instead.',
             DeprecationWarning,
             stacklevel=2,
         )
-        self.power_flow = value
+        self.electrical_flow = value
 
     @property
     def Q_th(self) -> Flow:  # noqa: N802
@@ -884,7 +884,7 @@ class HeatPumpWithSource(LinearConverter):
         cop: Coefficient of Performance (typically 1-20 range). Defines the ratio of
             thermal output to electrical input. The heat source extraction is automatically
             calculated as heat_source_flow = thermal_flow × (COP-1)/COP.
-        power_flow: Electrical input-flow representing electricity consumption for compressor.
+        electrical_flow: Electrical input-flow representing electricity consumption for compressor.
         heat_source_flow: Heat source input-flow representing thermal energy extracted from environment
             (ground, air, water source).
         thermal_flow: Thermal output-flow representing useful heat delivered to the application.
@@ -892,7 +892,7 @@ class HeatPumpWithSource(LinearConverter):
         meta_data: Used to store additional information. Not used internally but
             saved in results. Only use Python native types.
         COP: *Deprecated*. Use `cop` instead.
-        P_el: *Deprecated*. Use `power_flow` instead.
+        P_el: *Deprecated*. Use `electrical_flow` instead.
         Q_ab: *Deprecated*. Use `heat_source_flow` instead.
         Q_th: *Deprecated*. Use `thermal_flow` instead.
 
@@ -903,7 +903,7 @@ class HeatPumpWithSource(LinearConverter):
         ground_source_hp = HeatPumpWithSource(
             label='geothermal_heat_pump',
             cop=4.5,  # High COP due to stable ground temperature
-            power_flow=electricity_flow,
+            electrical_flow=electricity_flow,
             heat_source_flow=ground_heat_extraction,  # Heat extracted from ground loop
             thermal_flow=building_heating_flow,
         )
@@ -915,7 +915,7 @@ class HeatPumpWithSource(LinearConverter):
         waste_heat_pump = HeatPumpWithSource(
             label='waste_heat_pump',
             cop=temperature_dependent_cop,  # Varies with temperature of heat source
-            power_flow=electricity_consumption,
+            electrical_flow=electricity_consumption,
             heat_source_flow=industrial_heat_extraction,  # Heat extracted from a industrial process or waste water
             thermal_flow=heat_supply,
             on_off_parameters=OnOffParameters(
@@ -927,9 +927,9 @@ class HeatPumpWithSource(LinearConverter):
 
     Note:
         The conversion relationships are:
-        - thermal_flow = power_flow × COP (thermal output from electrical input)
+        - thermal_flow = electrical_flow × COP (thermal output from electrical input)
         - heat_source_flow = thermal_flow × (COP-1)/COP (heat source extraction)
-        - Energy balance: thermal_flow = power_flow + heat_source_flow
+        - Energy balance: thermal_flow = electrical_flow + heat_source_flow
 
         This formulation explicitly tracks the heat source, which is
         important for systems where the source capacity or temperature is limited,
@@ -943,7 +943,7 @@ def __init__(
         self,
         label: str,
         cop: Numeric_TPS | None = None,
-        power_flow: Flow | None = None,
+        electrical_flow: Flow | None = None,
         heat_source_flow: Flow | None = None,
         thermal_flow: Flow | None = None,
         on_off_parameters: OnOffParameters | None = None,
@@ -951,15 +951,15 @@ def __init__(
         **kwargs,
     ):
         # Handle deprecated parameters
-        power_flow = self._handle_deprecated_kwarg(kwargs, 'P_el', 'power_flow', power_flow)
+        electrical_flow = self._handle_deprecated_kwarg(kwargs, 'P_el', 'electrical_flow', electrical_flow)
         heat_source_flow = self._handle_deprecated_kwarg(kwargs, 'Q_ab', 'heat_source_flow', heat_source_flow)
         thermal_flow = self._handle_deprecated_kwarg(kwargs, 'Q_th', 'thermal_flow', thermal_flow)
         cop = self._handle_deprecated_kwarg(kwargs, 'COP', 'cop', cop)
         self._validate_kwargs(kwargs)
 
         # Validate required parameters
-        if power_flow is None:
-            raise ValueError(f"'{label}': power_flow is required and cannot be None")
+        if electrical_flow is None:
+            raise ValueError(f"'{label}': electrical_flow is required and cannot be None")
         if heat_source_flow is None:
             raise ValueError(f"'{label}': heat_source_flow is required and cannot be None")
         if thermal_flow is None:
@@ -969,19 +969,19 @@ def __init__(
 
         super().__init__(
             label,
-            inputs=[power_flow, heat_source_flow],
+            inputs=[electrical_flow, heat_source_flow],
             outputs=[thermal_flow],
             on_off_parameters=on_off_parameters,
             meta_data=meta_data,
         )
-        self.power_flow = power_flow
+        self.electrical_flow = electrical_flow
         self.heat_source_flow = heat_source_flow
         self.thermal_flow = thermal_flow
         self.cop = cop  # Uses setter
 
     @property
     def cop(self):
-        return self.conversion_factors[0][self.power_flow.label]
+        return self.conversion_factors[0][self.electrical_flow.label]
 
     @cop.setter
     def cop(self, value):
@@ -989,7 +989,7 @@ def cop(self, value):
         if np.any(np.asarray(value) == 1):
             raise ValueError(f'{self.label_full}.cop must be strictly !=1 for HeatPumpWithSource.')
         self.conversion_factors = [
-            {self.power_flow.label: value, self.thermal_flow.label: 1},
+            {self.electrical_flow.label: value, self.thermal_flow.label: 1},
             {self.heat_source_flow.label: value / (value - 1), self.thermal_flow.label: 1},
         ]
 
@@ -1014,20 +1014,20 @@ def COP(self, value: Numeric_TPS) -> None:  # noqa: N802
     @property
     def P_el(self) -> Flow:  # noqa: N802
         warnings.warn(
-            'The "P_el" property is deprecated. Use "power_flow" instead.',
+            'The "P_el" property is deprecated. Use "electrical_flow" instead.',
             DeprecationWarning,
             stacklevel=2,
         )
-        return self.power_flow
+        return self.electrical_flow
 
     @P_el.setter
     def P_el(self, value: Flow) -> None:  # noqa: N802
         warnings.warn(
-            'The "P_el" property is deprecated. Use "power_flow" instead.',
+            'The "P_el" property is deprecated. Use "electrical_flow" instead.',
             DeprecationWarning,
             stacklevel=2,
         )
-        self.power_flow = value
+        self.electrical_flow = value
 
     @property
     def Q_ab(self) -> Flow:  # noqa: N802

From f5d6ebee545ceb737c979e8270cf960bf061b947 Mon Sep 17 00:00:00 2001
From: FBumann <117816358+FBumann@users.noreply.github.com>
Date: Sun, 16 Nov 2025 10:39:59 +0100
Subject: [PATCH 14/25] Update CHANGELOG.md

---
 CHANGELOG.md | 29 ++++++++++++++++++++---------
 1 file changed, 20 insertions(+), 9 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7683da796..93df0ac28 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -75,23 +75,34 @@ If upgrading from v2.x, see the [v3.0.0 release notes](https://github.com/flixOp
 ### ♻️ Changed
 - **Code structure**: Removed `commons.py` module and moved all imports directly to `__init__.py` for cleaner code organization (no public API changes)
 - **Type handling improvements**: Updated internal data handling to work seamlessly with the new type system
-- **Parameter renaming in `linear_converters.py`**: Renamed parameters to use lowercase, descriptive names for better consistency:
-    - `Boiler`: `Q_fu` → `fuel_flow`, `Q_th` → `thermal_flow`
-    - `Power2Heat`: `P_el` → `electrical_flow`, `Q_th` → `thermal_flow`
-    - `HeatPump`: `COP` → `cop`, `P_el` → `electrical_flow`, `Q_th` → `thermal_flow`
-    - `CoolingTower`: `P_el` → `electrical_flow`, `Q_th` → `thermal_flow`
-    - `CHP`: `Q_fu` → `fuel_flow`, `P_el` → `electrical_flow`, `Q_th` → `thermal_flow`
-    - `HeatPumpWithSource`: `COP` → `cop`, `P_el` → `electrical_flow`, `Q_ab` → `heat_source_flow`, `Q_th` → `thermal_flow`
+- **Parameter renaming in `linear_converters.py`**: Renamed parameters to use lowercase, descriptive names for better consistency and clarity:
+    - **Flow parameters** (deprecated uppercase abbreviations → descriptive names):
+        - `Boiler`: `Q_fu` → `fuel_flow`, `Q_th` → `thermal_flow`
+        - `Power2Heat`: `P_el` → `power_flow` → `electrical_flow`, `Q_th` → `thermal_flow`
+        - `HeatPump`: `COP` → `cop`, `P_el` → `power_flow` → `electrical_flow`, `Q_th` → `thermal_flow`
+        - `CoolingTower`: `P_el` → `power_flow` → `electrical_flow`, `Q_th` → `thermal_flow`
+        - `CHP`: `Q_fu` → `fuel_flow`, `P_el` → `power_flow` → `electrical_flow`, `Q_th` → `thermal_flow`
+        - `HeatPumpWithSource`: `COP` → `cop`, `P_el` → `power_flow` → `electrical_flow`, `Q_ab` → `heat_source_flow`, `Q_th` → `thermal_flow`
+    - **Efficiency parameters** (abbreviated → descriptive names):
+        - `Boiler`: `eta` → `thermal_efficiency`
+        - `Power2Heat`: `eta` → `thermal_efficiency`
+        - `CHP`: `eta_th` → `thermal_efficiency`, `eta_el` → `electrical_efficiency`
+        - `HetaPump`: `COP` → `cop`
+        - `HetaPumpWithSource`: `COP` → `cop`
 
 ### 🗑️ Deprecated
-- **Old parameter names in `linear_converters.py`**: The old uppercase parameter names are now deprecated and accessible as properties that emit `DeprecationWarning`. They will be removed in v4.0.0:
-    - `Q_fu`, `Q_th`, `P_el`, `COP`, `Q_ab` (use lowercase equivalents instead)
+- **Old parameter names in `linear_converters.py`**: The following parameter names are now deprecated and accessible as properties/kwargs that emit `DeprecationWarning`. They will be removed in v4.0.0:
+    - **Flow parameters**: `Q_fu`, `Q_th`, `P_el`, `Q_ab`, `power_flow` (use `fuel_flow`, `thermal_flow`, `electrical_flow`, `heat_source_flow` instead)
+    - **Efficiency parameters**: `eta`, `eta_th`, `eta_el` (use `thermal_efficiency`, `electrical_efficiency` instead)
+    - **COP parameter**: `COP` (use lowercase `cop` instead)
 
 ### 🔥 Removed
 
 ### 🐛 Fixed
 - Fixed `ShareAllocationModel` inconsistency where None/inf conversion happened in `__init__` instead of during modeling, which could cause issues with parameter validation
 - Fixed numerous type hint inconsistencies across the codebase
+- Fixed backward compatibility issue in `HeatPump` and `HeatPumpWithSource` constructors where deprecated `COP` kwarg would fail before being handled
+- Fixed `check_bounds` function in `linear_converters.py` to use normalized array for comparisons, improving robustness with array-like inputs
 
 ### 🔒 Security
 

From 60b2bf6152f4b727c770019fa7d71f3ea51f7f8c Mon Sep 17 00:00:00 2001
From: FBumann <117816358+FBumann@users.noreply.github.com>
Date: Sun, 16 Nov 2025 10:58:44 +0100
Subject: [PATCH 15/25] Update all tests and examples

---
 examples/00_Minmal/minimal_example.py         |  6 +-
 examples/01_Simple/simple_example.py          | 16 ++---
 examples/02_Complex/complex_example.py        | 16 ++---
 .../example_calculation_types.py              | 16 ++---
 examples/04_Scenarios/scenario_example.py     | 18 ++---
 .../two_stage_optimization.py                 | 16 ++---
 tests/conftest.py                             | 48 ++++++-------
 tests/test_component.py                       | 27 +++++---
 tests/test_effect.py                          |  6 +-
 tests/test_flow_system_resample.py            |  4 +-
 tests/test_functional.py                      | 68 +++++++++----------
 tests/test_scenarios.py                       |  6 +-
 12 files changed, 129 insertions(+), 118 deletions(-)

diff --git a/examples/00_Minmal/minimal_example.py b/examples/00_Minmal/minimal_example.py
index 92e6801b2..9756396b3 100644
--- a/examples/00_Minmal/minimal_example.py
+++ b/examples/00_Minmal/minimal_example.py
@@ -18,9 +18,9 @@
         fx.Effect('Costs', '€', 'Cost', is_standard=True, is_objective=True),
         fx.linear_converters.Boiler(
             'Boiler',
-            eta=0.5,
-            Q_th=fx.Flow(label='Heat', bus='Heat', size=50),
-            Q_fu=fx.Flow(label='Gas', bus='Gas'),
+            thermal_efficiency=0.5,
+            thermal_flow=fx.Flow(label='Heat', bus='Heat', size=50),
+            fuel_flow=fx.Flow(label='Gas', bus='Gas'),
         ),
         fx.Sink(
             'Sink',
diff --git a/examples/01_Simple/simple_example.py b/examples/01_Simple/simple_example.py
index fd5a3d9b7..d9737cf7b 100644
--- a/examples/01_Simple/simple_example.py
+++ b/examples/01_Simple/simple_example.py
@@ -46,19 +46,19 @@
     # Boiler: Converts fuel (gas) into thermal energy (heat)
     boiler = fx.linear_converters.Boiler(
         label='Boiler',
-        eta=0.5,
-        Q_th=fx.Flow(label='Q_th', bus='Fernwärme', size=50, relative_minimum=0.1, relative_maximum=1),
-        Q_fu=fx.Flow(label='Q_fu', bus='Gas'),
+        thermal_efficiency=0.5,
+        thermal_flow=fx.Flow(label='Q_th', bus='Fernwärme', size=50, relative_minimum=0.1, relative_maximum=1),
+        fuel_flow=fx.Flow(label='Q_fu', bus='Gas'),
     )
 
     # Combined Heat and Power (CHP): Generates both electricity and heat from fuel
     chp = fx.linear_converters.CHP(
         label='CHP',
-        eta_th=0.5,
-        eta_el=0.4,
-        P_el=fx.Flow('P_el', bus='Strom', size=60, relative_minimum=5 / 60),
-        Q_th=fx.Flow('Q_th', bus='Fernwärme'),
-        Q_fu=fx.Flow('Q_fu', bus='Gas'),
+        thermal_efficiency=0.5,
+        electrical_efficiency=0.4,
+        electrical_flow=fx.Flow('P_el', bus='Strom', size=60, relative_minimum=5 / 60),
+        thermal_flow=fx.Flow('Q_th', bus='Fernwärme'),
+        fuel_flow=fx.Flow('Q_fu', bus='Gas'),
     )
 
     # Storage: Energy storage system with charging and discharging capabilities
diff --git a/examples/02_Complex/complex_example.py b/examples/02_Complex/complex_example.py
index 3ff5b251c..0f7ca0b82 100644
--- a/examples/02_Complex/complex_example.py
+++ b/examples/02_Complex/complex_example.py
@@ -50,11 +50,11 @@
     # A gas boiler that converts fuel into thermal output, with investment and on-off parameters
     Gaskessel = fx.linear_converters.Boiler(
         'Kessel',
-        eta=0.5,  # Efficiency ratio
+        thermal_efficiency=0.5,  # Efficiency ratio
         on_off_parameters=fx.OnOffParameters(
             effects_per_running_hour={Costs.label: 0, CO2.label: 1000}
         ),  # CO2 emissions per hour
-        Q_th=fx.Flow(
+        thermal_flow=fx.Flow(
             label='Q_th',  # Thermal output
             bus='Fernwärme',  # Linked bus
             size=fx.InvestParameters(
@@ -79,19 +79,19 @@
                 switch_on_total_max=1000,  # Max number of starts
             ),
         ),
-        Q_fu=fx.Flow(label='Q_fu', bus='Gas', size=200),
+        fuel_flow=fx.Flow(label='Q_fu', bus='Gas', size=200),
     )
 
     # 2. Define CHP Unit
     # Combined Heat and Power unit that generates both electricity and heat from fuel
     bhkw = fx.linear_converters.CHP(
         'BHKW2',
-        eta_th=0.5,
-        eta_el=0.4,
+        thermal_efficiency=0.5,
+        electrical_efficiency=0.4,
         on_off_parameters=fx.OnOffParameters(effects_per_switch_on=0.01),
-        P_el=fx.Flow('P_el', bus='Strom', size=60, relative_minimum=5 / 60),
-        Q_th=fx.Flow('Q_th', bus='Fernwärme', size=1e3),
-        Q_fu=fx.Flow('Q_fu', bus='Gas', size=1e3, previous_flow_rate=20),  # The CHP was ON previously
+        electrical_flow=fx.Flow('P_el', bus='Strom', size=60, relative_minimum=5 / 60),
+        thermal_flow=fx.Flow('Q_th', bus='Fernwärme', size=1e3),
+        fuel_flow=fx.Flow('Q_fu', bus='Gas', size=1e3, previous_flow_rate=20),  # The CHP was ON previously
     )
 
     # 3. Define CHP with Piecewise Conversion
diff --git a/examples/03_Calculation_types/example_calculation_types.py b/examples/03_Calculation_types/example_calculation_types.py
index e339c1c24..fa57e6f9a 100644
--- a/examples/03_Calculation_types/example_calculation_types.py
+++ b/examples/03_Calculation_types/example_calculation_types.py
@@ -71,9 +71,9 @@
     # 1. Boiler
     a_gaskessel = fx.linear_converters.Boiler(
         'Kessel',
-        eta=0.85,
-        Q_th=fx.Flow(label='Q_th', bus='Fernwärme'),
-        Q_fu=fx.Flow(
+        thermal_efficiency=0.85,
+        thermal_flow=fx.Flow(label='Q_th', bus='Fernwärme'),
+        fuel_flow=fx.Flow(
             label='Q_fu',
             bus='Gas',
             size=95,
@@ -86,12 +86,12 @@
     # 2. CHP
     a_kwk = fx.linear_converters.CHP(
         'BHKW2',
-        eta_th=0.58,
-        eta_el=0.22,
+        thermal_efficiency=0.58,
+        electrical_efficiency=0.22,
         on_off_parameters=fx.OnOffParameters(effects_per_switch_on=24000),
-        P_el=fx.Flow('P_el', bus='Strom', size=200),
-        Q_th=fx.Flow('Q_th', bus='Fernwärme', size=200),
-        Q_fu=fx.Flow('Q_fu', bus='Kohle', size=288, relative_minimum=87 / 288, previous_flow_rate=100),
+        electrical_flow=fx.Flow('P_el', bus='Strom', size=200),
+        thermal_flow=fx.Flow('Q_th', bus='Fernwärme', size=200),
+        fuel_flow=fx.Flow('Q_fu', bus='Kohle', size=288, relative_minimum=87 / 288, previous_flow_rate=100),
     )
 
     # 3. Storage
diff --git a/examples/04_Scenarios/scenario_example.py b/examples/04_Scenarios/scenario_example.py
index bf4f24617..ca50876c7 100644
--- a/examples/04_Scenarios/scenario_example.py
+++ b/examples/04_Scenarios/scenario_example.py
@@ -114,8 +114,8 @@
     # Modern condensing gas boiler with realistic efficiency
     boiler = fx.linear_converters.Boiler(
         label='Boiler',
-        eta=0.92,  # Realistic efficiency for modern condensing gas boiler (92%)
-        Q_th=fx.Flow(
+        thermal_efficiency=0.92,  # Realistic efficiency for modern condensing gas boiler (92%)
+        thermal_flow=fx.Flow(
             label='Q_th',
             bus='Fernwärme',
             size=50,
@@ -123,18 +123,20 @@
             relative_maximum=1,
             on_off_parameters=fx.OnOffParameters(),
         ),
-        Q_fu=fx.Flow(label='Q_fu', bus='Gas'),
+        fuel_flow=fx.Flow(label='Q_fu', bus='Gas'),
     )
 
     # Combined Heat and Power (CHP): Generates both electricity and heat from fuel
     # Modern CHP unit with realistic efficiencies (total efficiency ~88%)
     chp = fx.linear_converters.CHP(
         label='CHP',
-        eta_th=0.48,  # Realistic thermal efficiency (48%)
-        eta_el=0.40,  # Realistic electrical efficiency (40%)
-        P_el=fx.Flow('P_el', bus='Strom', size=60, relative_minimum=5 / 60, on_off_parameters=fx.OnOffParameters()),
-        Q_th=fx.Flow('Q_th', bus='Fernwärme'),
-        Q_fu=fx.Flow('Q_fu', bus='Gas'),
+        thermal_efficiency=0.48,  # Realistic thermal efficiency (48%)
+        electrical_efficiency=0.40,  # Realistic electrical efficiency (40%)
+        electrical_flow=fx.Flow(
+            'P_el', bus='Strom', size=60, relative_minimum=5 / 60, on_off_parameters=fx.OnOffParameters()
+        ),
+        thermal_flow=fx.Flow('Q_th', bus='Fernwärme'),
+        fuel_flow=fx.Flow('Q_fu', bus='Gas'),
     )
 
     # Storage: Thermal energy storage system with charging and discharging capabilities
diff --git a/examples/05_Two-stage-optimization/two_stage_optimization.py b/examples/05_Two-stage-optimization/two_stage_optimization.py
index 7354cb877..39a3aea0b 100644
--- a/examples/05_Two-stage-optimization/two_stage_optimization.py
+++ b/examples/05_Two-stage-optimization/two_stage_optimization.py
@@ -45,9 +45,9 @@
         fx.Effect('PE', 'kWh_PE', 'Primärenergie'),
         fx.linear_converters.Boiler(
             'Kessel',
-            eta=0.85,
-            Q_th=fx.Flow(label='Q_th', bus='Fernwärme'),
-            Q_fu=fx.Flow(
+            thermal_efficiency=0.85,
+            thermal_flow=fx.Flow(label='Q_th', bus='Fernwärme'),
+            fuel_flow=fx.Flow(
                 label='Q_fu',
                 bus='Gas',
                 size=fx.InvestParameters(
@@ -60,14 +60,14 @@
         ),
         fx.linear_converters.CHP(
             'BHKW2',
-            eta_th=0.58,
-            eta_el=0.22,
+            thermal_efficiency=0.58,
+            electrical_efficiency=0.22,
             on_off_parameters=fx.OnOffParameters(
                 effects_per_switch_on=1_000, consecutive_on_hours_min=10, consecutive_off_hours_min=10
             ),
-            P_el=fx.Flow('P_el', bus='Strom'),
-            Q_th=fx.Flow('Q_th', bus='Fernwärme'),
-            Q_fu=fx.Flow(
+            electrical_flow=fx.Flow('P_el', bus='Strom'),
+            thermal_flow=fx.Flow('Q_th', bus='Fernwärme'),
+            fuel_flow=fx.Flow(
                 'Q_fu',
                 bus='Kohle',
                 size=fx.InvestParameters(
diff --git a/tests/conftest.py b/tests/conftest.py
index bd940b843..1873bab0e 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -131,8 +131,8 @@ def simple():
             """Simple boiler from simple_flow_system"""
             return fx.linear_converters.Boiler(
                 'Boiler',
-                eta=0.5,
-                Q_th=fx.Flow(
+                thermal_efficiency=0.5,
+                thermal_flow=fx.Flow(
                     'Q_th',
                     bus='Fernwärme',
                     size=50,
@@ -140,7 +140,7 @@ def simple():
                     relative_maximum=1,
                     on_off_parameters=fx.OnOffParameters(),
                 ),
-                Q_fu=fx.Flow('Q_fu', bus='Gas'),
+                fuel_flow=fx.Flow('Q_fu', bus='Gas'),
             )
 
         @staticmethod
@@ -148,9 +148,9 @@ def complex():
             """Complex boiler with investment parameters from flow_system_complex"""
             return fx.linear_converters.Boiler(
                 'Kessel',
-                eta=0.5,
+                thermal_efficiency=0.5,
                 on_off_parameters=fx.OnOffParameters(effects_per_running_hour={'costs': 0, 'CO2': 1000}),
-                Q_th=fx.Flow(
+                thermal_flow=fx.Flow(
                     'Q_th',
                     bus='Fernwärme',
                     load_factor_max=1.0,
@@ -175,7 +175,7 @@ def complex():
                     ),
                     flow_hours_total_max=1e6,
                 ),
-                Q_fu=fx.Flow('Q_fu', bus='Gas', size=200, relative_minimum=0, relative_maximum=1),
+                fuel_flow=fx.Flow('Q_fu', bus='Gas', size=200, relative_minimum=0, relative_maximum=1),
             )
 
     class CHPs:
@@ -184,13 +184,13 @@ def simple():
             """Simple CHP from simple_flow_system"""
             return fx.linear_converters.CHP(
                 'CHP_unit',
-                eta_th=0.5,
-                eta_el=0.4,
-                P_el=fx.Flow(
+                thermal_efficiency=0.5,
+                electrical_efficiency=0.4,
+                electrical_flow=fx.Flow(
                     'P_el', bus='Strom', size=60, relative_minimum=5 / 60, on_off_parameters=fx.OnOffParameters()
                 ),
-                Q_th=fx.Flow('Q_th', bus='Fernwärme'),
-                Q_fu=fx.Flow('Q_fu', bus='Gas'),
+                thermal_flow=fx.Flow('Q_th', bus='Fernwärme'),
+                fuel_flow=fx.Flow('Q_fu', bus='Gas'),
             )
 
         @staticmethod
@@ -198,12 +198,12 @@ def base():
             """CHP from flow_system_base"""
             return fx.linear_converters.CHP(
                 'KWK',
-                eta_th=0.5,
-                eta_el=0.4,
+                thermal_efficiency=0.5,
+                electrical_efficiency=0.4,
                 on_off_parameters=fx.OnOffParameters(effects_per_switch_on=0.01),
-                P_el=fx.Flow('P_el', bus='Strom', size=60, relative_minimum=5 / 60, previous_flow_rate=10),
-                Q_th=fx.Flow('Q_th', bus='Fernwärme', size=1e3),
-                Q_fu=fx.Flow('Q_fu', bus='Gas', size=1e3),
+                electrical_flow=fx.Flow('P_el', bus='Strom', size=60, relative_minimum=5 / 60, previous_flow_rate=10),
+                thermal_flow=fx.Flow('Q_th', bus='Fernwärme', size=1e3),
+                fuel_flow=fx.Flow('Q_fu', bus='Gas', size=1e3),
             )
 
     class LinearConverters:
@@ -596,9 +596,9 @@ def flow_system_long():
     flow_system.add_elements(
         fx.linear_converters.Boiler(
             'Kessel',
-            eta=0.85,
-            Q_th=fx.Flow(label='Q_th', bus='Fernwärme'),
-            Q_fu=fx.Flow(
+            thermal_efficiency=0.85,
+            thermal_flow=fx.Flow(label='Q_th', bus='Fernwärme'),
+            fuel_flow=fx.Flow(
                 label='Q_fu',
                 bus='Gas',
                 size=95,
@@ -609,12 +609,12 @@ def flow_system_long():
         ),
         fx.linear_converters.CHP(
             'BHKW2',
-            eta_th=0.58,
-            eta_el=0.22,
+            thermal_efficiency=0.58,
+            electrical_efficiency=0.22,
             on_off_parameters=fx.OnOffParameters(effects_per_switch_on=24000),
-            P_el=fx.Flow('P_el', bus='Strom'),
-            Q_th=fx.Flow('Q_th', bus='Fernwärme'),
-            Q_fu=fx.Flow('Q_fu', bus='Kohle', size=288, relative_minimum=87 / 288),
+            electrical_flow=fx.Flow('P_el', bus='Strom'),
+            thermal_flow=fx.Flow('Q_th', bus='Fernwärme'),
+            fuel_flow=fx.Flow('Q_fu', bus='Kohle', size=288, relative_minimum=87 / 288),
         ),
         fx.Storage(
             'Speicher',
diff --git a/tests/test_component.py b/tests/test_component.py
index be1eecf3b..dbbd85c8f 100644
--- a/tests/test_component.py
+++ b/tests/test_component.py
@@ -416,7 +416,10 @@ def test_transmission_basic(self, basic_flow_system, highs_solver):
         flow_system.add_elements(fx.Bus('Wärme lokal'))
 
         boiler = fx.linear_converters.Boiler(
-            'Boiler', eta=0.5, Q_th=fx.Flow('Q_th', bus='Wärme lokal'), Q_fu=fx.Flow('Q_fu', bus='Gas')
+            'Boiler',
+            thermal_efficiency=0.5,
+            thermal_flow=fx.Flow('Q_th', bus='Wärme lokal'),
+            fuel_flow=fx.Flow('Q_fu', bus='Gas'),
         )
 
         transmission = fx.Transmission(
@@ -453,13 +456,16 @@ def test_transmission_balanced(self, basic_flow_system, highs_solver):
 
         boiler = fx.linear_converters.Boiler(
             'Boiler_Standard',
-            eta=0.9,
-            Q_th=fx.Flow('Q_th', bus='Fernwärme', relative_maximum=np.array([0, 0, 0, 1, 1, 1, 1, 1, 1, 1])),
-            Q_fu=fx.Flow('Q_fu', bus='Gas'),
+            thermal_efficiency=0.9,
+            thermal_flow=fx.Flow('Q_th', bus='Fernwärme', relative_maximum=np.array([0, 0, 0, 1, 1, 1, 1, 1, 1, 1])),
+            fuel_flow=fx.Flow('Q_fu', bus='Gas'),
         )
 
         boiler2 = fx.linear_converters.Boiler(
-            'Boiler_backup', eta=0.4, Q_th=fx.Flow('Q_th', bus='Wärme lokal'), Q_fu=fx.Flow('Q_fu', bus='Gas')
+            'Boiler_backup',
+            thermal_efficiency=0.4,
+            thermal_flow=fx.Flow('Q_th', bus='Wärme lokal'),
+            fuel_flow=fx.Flow('Q_fu', bus='Gas'),
         )
 
         last2 = fx.Sink(
@@ -527,13 +533,16 @@ def test_transmission_unbalanced(self, basic_flow_system, highs_solver):
 
         boiler = fx.linear_converters.Boiler(
             'Boiler_Standard',
-            eta=0.9,
-            Q_th=fx.Flow('Q_th', bus='Fernwärme', relative_maximum=np.array([0, 0, 0, 1, 1, 1, 1, 1, 1, 1])),
-            Q_fu=fx.Flow('Q_fu', bus='Gas'),
+            thermal_efficiency=0.9,
+            thermal_flow=fx.Flow('Q_th', bus='Fernwärme', relative_maximum=np.array([0, 0, 0, 1, 1, 1, 1, 1, 1, 1])),
+            fuel_flow=fx.Flow('Q_fu', bus='Gas'),
         )
 
         boiler2 = fx.linear_converters.Boiler(
-            'Boiler_backup', eta=0.4, Q_th=fx.Flow('Q_th', bus='Wärme lokal'), Q_fu=fx.Flow('Q_fu', bus='Gas')
+            'Boiler_backup',
+            thermal_efficiency=0.4,
+            thermal_flow=fx.Flow('Q_th', bus='Wärme lokal'),
+            fuel_flow=fx.Flow('Q_fu', bus='Gas'),
         )
 
         last2 = fx.Sink(
diff --git a/tests/test_effect.py b/tests/test_effect.py
index cd3edc537..8293ec62f 100644
--- a/tests/test_effect.py
+++ b/tests/test_effect.py
@@ -247,13 +247,13 @@ def test_shares(self, basic_flow_system_linopy_coords, coords_config):
             effect3,
             fx.linear_converters.Boiler(
                 'Boiler',
-                eta=0.5,
-                Q_th=fx.Flow(
+                thermal_efficiency=0.5,
+                thermal_flow=fx.Flow(
                     'Q_th',
                     bus='Fernwärme',
                     size=fx.InvestParameters(effects_of_investment_per_size=10, minimum_size=20, mandatory=True),
                 ),
-                Q_fu=fx.Flow('Q_fu', bus='Gas'),
+                fuel_flow=fx.Flow('Q_fu', bus='Gas'),
             ),
         )
 
diff --git a/tests/test_flow_system_resample.py b/tests/test_flow_system_resample.py
index d28872a0f..8946dd02f 100644
--- a/tests/test_flow_system_resample.py
+++ b/tests/test_flow_system_resample.py
@@ -52,9 +52,9 @@ def complex_fs():
 
     # Piecewise converter
     converter = fx.linear_converters.Boiler(
-        'boiler', eta=0.9, Q_fu=fx.Flow('gas', bus='elec'), Q_th=fx.Flow('heat', bus='heat')
+        'boiler', thermal_efficiency=0.9, fuel_flow=fx.Flow('gas', bus='elec'), thermal_flow=fx.Flow('heat', bus='heat')
     )
-    converter.Q_th.size = 100
+    converter.thermal_flow.size = 100
     fs.add_elements(converter)
 
     # Component with investment
diff --git a/tests/test_functional.py b/tests/test_functional.py
index a83bf112f..6fe272a1a 100644
--- a/tests/test_functional.py
+++ b/tests/test_functional.py
@@ -86,8 +86,8 @@ def flow_system_minimal(timesteps) -> fx.FlowSystem:
         fx.linear_converters.Boiler(
             'Boiler',
             0.5,
-            Q_fu=fx.Flow('Q_fu', bus='Gas'),
-            Q_th=fx.Flow('Q_th', bus='Fernwärme'),
+            fuel_flow=fx.Flow('Q_fu', bus='Gas'),
+            thermal_flow=fx.Flow('Q_th', bus='Fernwärme'),
         )
     )
     return flow_system
@@ -142,8 +142,8 @@ def test_fixed_size(solver_fixture, time_steps_fixture):
         fx.linear_converters.Boiler(
             'Boiler',
             0.5,
-            Q_fu=fx.Flow('Q_fu', bus='Gas'),
-            Q_th=fx.Flow(
+            fuel_flow=fx.Flow('Q_fu', bus='Gas'),
+            thermal_flow=fx.Flow(
                 'Q_th',
                 bus='Fernwärme',
                 size=fx.InvestParameters(fixed_size=1000, effects_of_investment=10, effects_of_investment_per_size=1),
@@ -183,8 +183,8 @@ def test_optimize_size(solver_fixture, time_steps_fixture):
         fx.linear_converters.Boiler(
             'Boiler',
             0.5,
-            Q_fu=fx.Flow('Q_fu', bus='Gas'),
-            Q_th=fx.Flow(
+            fuel_flow=fx.Flow('Q_fu', bus='Gas'),
+            thermal_flow=fx.Flow(
                 'Q_th',
                 bus='Fernwärme',
                 size=fx.InvestParameters(effects_of_investment=10, effects_of_investment_per_size=1),
@@ -224,8 +224,8 @@ def test_size_bounds(solver_fixture, time_steps_fixture):
         fx.linear_converters.Boiler(
             'Boiler',
             0.5,
-            Q_fu=fx.Flow('Q_fu', bus='Gas'),
-            Q_th=fx.Flow(
+            fuel_flow=fx.Flow('Q_fu', bus='Gas'),
+            thermal_flow=fx.Flow(
                 'Q_th',
                 bus='Fernwärme',
                 size=fx.InvestParameters(minimum_size=40, effects_of_investment=10, effects_of_investment_per_size=1),
@@ -265,8 +265,8 @@ def test_optional_invest(solver_fixture, time_steps_fixture):
         fx.linear_converters.Boiler(
             'Boiler',
             0.5,
-            Q_fu=fx.Flow('Q_fu', bus='Gas'),
-            Q_th=fx.Flow(
+            fuel_flow=fx.Flow('Q_fu', bus='Gas'),
+            thermal_flow=fx.Flow(
                 'Q_th',
                 bus='Fernwärme',
                 size=fx.InvestParameters(
@@ -277,8 +277,8 @@ def test_optional_invest(solver_fixture, time_steps_fixture):
         fx.linear_converters.Boiler(
             'Boiler_optional',
             0.5,
-            Q_fu=fx.Flow('Q_fu', bus='Gas'),
-            Q_th=fx.Flow(
+            fuel_flow=fx.Flow('Q_fu', bus='Gas'),
+            thermal_flow=fx.Flow(
                 'Q_th',
                 bus='Fernwärme',
                 size=fx.InvestParameters(
@@ -337,8 +337,8 @@ def test_on(solver_fixture, time_steps_fixture):
         fx.linear_converters.Boiler(
             'Boiler',
             0.5,
-            Q_fu=fx.Flow('Q_fu', bus='Gas'),
-            Q_th=fx.Flow('Q_th', bus='Fernwärme', size=100, on_off_parameters=fx.OnOffParameters()),
+            fuel_flow=fx.Flow('Q_fu', bus='Gas'),
+            thermal_flow=fx.Flow('Q_th', bus='Fernwärme', size=100, on_off_parameters=fx.OnOffParameters()),
         )
     )
 
@@ -376,8 +376,8 @@ def test_off(solver_fixture, time_steps_fixture):
         fx.linear_converters.Boiler(
             'Boiler',
             0.5,
-            Q_fu=fx.Flow('Q_fu', bus='Gas'),
-            Q_th=fx.Flow(
+            fuel_flow=fx.Flow('Q_fu', bus='Gas'),
+            thermal_flow=fx.Flow(
                 'Q_th',
                 bus='Fernwärme',
                 size=100,
@@ -427,8 +427,8 @@ def test_switch_on_off(solver_fixture, time_steps_fixture):
         fx.linear_converters.Boiler(
             'Boiler',
             0.5,
-            Q_fu=fx.Flow('Q_fu', bus='Gas'),
-            Q_th=fx.Flow(
+            fuel_flow=fx.Flow('Q_fu', bus='Gas'),
+            thermal_flow=fx.Flow(
                 'Q_th',
                 bus='Fernwärme',
                 size=100,
@@ -485,8 +485,8 @@ def test_on_total_max(solver_fixture, time_steps_fixture):
         fx.linear_converters.Boiler(
             'Boiler',
             0.5,
-            Q_fu=fx.Flow('Q_fu', bus='Gas'),
-            Q_th=fx.Flow(
+            fuel_flow=fx.Flow('Q_fu', bus='Gas'),
+            thermal_flow=fx.Flow(
                 'Q_th',
                 bus='Fernwärme',
                 size=100,
@@ -496,8 +496,8 @@ def test_on_total_max(solver_fixture, time_steps_fixture):
         fx.linear_converters.Boiler(
             'Boiler_backup',
             0.2,
-            Q_fu=fx.Flow('Q_fu', bus='Gas'),
-            Q_th=fx.Flow('Q_th', bus='Fernwärme', size=100),
+            fuel_flow=fx.Flow('Q_fu', bus='Gas'),
+            thermal_flow=fx.Flow('Q_th', bus='Fernwärme', size=100),
         ),
     )
 
@@ -535,8 +535,8 @@ def test_on_total_bounds(solver_fixture, time_steps_fixture):
         fx.linear_converters.Boiler(
             'Boiler',
             0.5,
-            Q_fu=fx.Flow('Q_fu', bus='Gas'),
-            Q_th=fx.Flow(
+            fuel_flow=fx.Flow('Q_fu', bus='Gas'),
+            thermal_flow=fx.Flow(
                 'Q_th',
                 bus='Fernwärme',
                 size=100,
@@ -546,8 +546,8 @@ def test_on_total_bounds(solver_fixture, time_steps_fixture):
         fx.linear_converters.Boiler(
             'Boiler_backup',
             0.2,
-            Q_fu=fx.Flow('Q_fu', bus='Gas'),
-            Q_th=fx.Flow(
+            fuel_flow=fx.Flow('Q_fu', bus='Gas'),
+            thermal_flow=fx.Flow(
                 'Q_th',
                 bus='Fernwärme',
                 size=100,
@@ -609,8 +609,8 @@ def test_consecutive_on_off(solver_fixture, time_steps_fixture):
         fx.linear_converters.Boiler(
             'Boiler',
             0.5,
-            Q_fu=fx.Flow('Q_fu', bus='Gas'),
-            Q_th=fx.Flow(
+            fuel_flow=fx.Flow('Q_fu', bus='Gas'),
+            thermal_flow=fx.Flow(
                 'Q_th',
                 bus='Fernwärme',
                 size=100,
@@ -620,8 +620,8 @@ def test_consecutive_on_off(solver_fixture, time_steps_fixture):
         fx.linear_converters.Boiler(
             'Boiler_backup',
             0.2,
-            Q_fu=fx.Flow('Q_fu', bus='Gas'),
-            Q_th=fx.Flow('Q_th', bus='Fernwärme', size=100),
+            fuel_flow=fx.Flow('Q_fu', bus='Gas'),
+            thermal_flow=fx.Flow('Q_th', bus='Fernwärme', size=100),
         ),
     )
     flow_system['Wärmelast'].inputs[0].fixed_relative_profile = np.array([5, 10, 20, 18, 12])
@@ -670,14 +670,14 @@ def test_consecutive_off(solver_fixture, time_steps_fixture):
         fx.linear_converters.Boiler(
             'Boiler',
             0.5,
-            Q_fu=fx.Flow('Q_fu', bus='Gas'),
-            Q_th=fx.Flow('Q_th', bus='Fernwärme'),
+            fuel_flow=fx.Flow('Q_fu', bus='Gas'),
+            thermal_flow=fx.Flow('Q_th', bus='Fernwärme'),
         ),
         fx.linear_converters.Boiler(
             'Boiler_backup',
             0.2,
-            Q_fu=fx.Flow('Q_fu', bus='Gas'),
-            Q_th=fx.Flow(
+            fuel_flow=fx.Flow('Q_fu', bus='Gas'),
+            thermal_flow=fx.Flow(
                 'Q_th',
                 bus='Fernwärme',
                 size=100,
diff --git a/tests/test_scenarios.py b/tests/test_scenarios.py
index 928eb88c6..c25750259 100644
--- a/tests/test_scenarios.py
+++ b/tests/test_scenarios.py
@@ -139,9 +139,9 @@ def flow_system_complex_scenarios() -> fx.FlowSystem:
 
     boiler = fx.linear_converters.Boiler(
         'Kessel',
-        eta=0.5,
+        thermal_efficiency=0.5,
         on_off_parameters=fx.OnOffParameters(effects_per_running_hour={'costs': 0, 'CO2': 1000}),
-        Q_th=fx.Flow(
+        thermal_flow=fx.Flow(
             'Q_th',
             bus='Fernwärme',
             load_factor_max=1.0,
@@ -166,7 +166,7 @@ def flow_system_complex_scenarios() -> fx.FlowSystem:
             ),
             flow_hours_total_max=1e6,
         ),
-        Q_fu=fx.Flow('Q_fu', bus='Gas', size=200, relative_minimum=0, relative_maximum=1),
+        fuel_flow=fx.Flow('Q_fu', bus='Gas', size=200, relative_minimum=0, relative_maximum=1),
     )
 
     invest_speicher = fx.InvestParameters(

From 56664703fa2e1b2237db4efdc8aa86eeb83e2df9 Mon Sep 17 00:00:00 2001
From: FBumann <117816358+FBumann@users.noreply.github.com>
Date: Sun, 16 Nov 2025 17:34:41 +0100
Subject: [PATCH 16/25] Update remaining tests

---
 tests/test_functional.py  | 66 +++++++++++++++++++--------------------
 tests/test_integration.py |  6 ++--
 2 files changed, 36 insertions(+), 36 deletions(-)

diff --git a/tests/test_functional.py b/tests/test_functional.py
index 6fe272a1a..36274d494 100644
--- a/tests/test_functional.py
+++ b/tests/test_functional.py
@@ -162,14 +162,14 @@ def test_fixed_size(solver_fixture, time_steps_fixture):
         err_msg='The total costs does not have the right value',
     )
     assert_allclose(
-        boiler.Q_th.submodel._investment.size.solution.item(),
+        boiler.thermal_flow.submodel._investment.size.solution.item(),
         1000,
         rtol=1e-5,
         atol=1e-10,
         err_msg='"Boiler__Q_th__Investment_size" does not have the right value',
     )
     assert_allclose(
-        boiler.Q_th.submodel._investment.invested.solution.item(),
+        boiler.thermal_flow.submodel._investment.invested.solution.item(),
         1,
         rtol=1e-5,
         atol=1e-10,
@@ -203,14 +203,14 @@ def test_optimize_size(solver_fixture, time_steps_fixture):
         err_msg='The total costs does not have the right value',
     )
     assert_allclose(
-        boiler.Q_th.submodel._investment.size.solution.item(),
+        boiler.thermal_flow.submodel._investment.size.solution.item(),
         20,
         rtol=1e-5,
         atol=1e-10,
         err_msg='"Boiler__Q_th__Investment_size" does not have the right value',
     )
     assert_allclose(
-        boiler.Q_th.submodel._investment.invested.solution.item(),
+        boiler.thermal_flow.submodel._investment.invested.solution.item(),
         1,
         rtol=1e-5,
         atol=1e-10,
@@ -244,14 +244,14 @@ def test_size_bounds(solver_fixture, time_steps_fixture):
         err_msg='The total costs does not have the right value',
     )
     assert_allclose(
-        boiler.Q_th.submodel._investment.size.solution.item(),
+        boiler.thermal_flow.submodel._investment.size.solution.item(),
         40,
         rtol=1e-5,
         atol=1e-10,
         err_msg='"Boiler__Q_th__Investment_size" does not have the right value',
     )
     assert_allclose(
-        boiler.Q_th.submodel._investment.invested.solution.item(),
+        boiler.thermal_flow.submodel._investment.invested.solution.item(),
         1,
         rtol=1e-5,
         atol=1e-10,
@@ -300,14 +300,14 @@ def test_optional_invest(solver_fixture, time_steps_fixture):
         err_msg='The total costs does not have the right value',
     )
     assert_allclose(
-        boiler.Q_th.submodel._investment.size.solution.item(),
+        boiler.thermal_flow.submodel._investment.size.solution.item(),
         40,
         rtol=1e-5,
         atol=1e-10,
         err_msg='"Boiler__Q_th__Investment_size" does not have the right value',
     )
     assert_allclose(
-        boiler.Q_th.submodel._investment.invested.solution.item(),
+        boiler.thermal_flow.submodel._investment.invested.solution.item(),
         1,
         rtol=1e-5,
         atol=1e-10,
@@ -315,14 +315,14 @@ def test_optional_invest(solver_fixture, time_steps_fixture):
     )
 
     assert_allclose(
-        boiler_optional.Q_th.submodel._investment.size.solution.item(),
+        boiler_optional.thermal_flow.submodel._investment.size.solution.item(),
         0,
         rtol=1e-5,
         atol=1e-10,
         err_msg='"Boiler__Q_th__Investment_size" does not have the right value',
     )
     assert_allclose(
-        boiler_optional.Q_th.submodel._investment.invested.solution.item(),
+        boiler_optional.thermal_flow.submodel._investment.invested.solution.item(),
         0,
         rtol=1e-5,
         atol=1e-10,
@@ -354,14 +354,14 @@ def test_on(solver_fixture, time_steps_fixture):
     )
 
     assert_allclose(
-        boiler.Q_th.submodel.on_off.on.solution.values,
+        boiler.thermal_flow.submodel.on_off.on.solution.values,
         [0, 1, 1, 0, 1],
         rtol=1e-5,
         atol=1e-10,
         err_msg='"Boiler__Q_th__on" does not have the right value',
     )
     assert_allclose(
-        boiler.Q_th.submodel.flow_rate.solution.values,
+        boiler.thermal_flow.submodel.flow_rate.solution.values,
         [0, 10, 20, 0, 10],
         rtol=1e-5,
         atol=1e-10,
@@ -398,21 +398,21 @@ def test_off(solver_fixture, time_steps_fixture):
     )
 
     assert_allclose(
-        boiler.Q_th.submodel.on_off.on.solution.values,
+        boiler.thermal_flow.submodel.on_off.on.solution.values,
         [0, 1, 1, 0, 1],
         rtol=1e-5,
         atol=1e-10,
         err_msg='"Boiler__Q_th__on" does not have the right value',
     )
     assert_allclose(
-        boiler.Q_th.submodel.on_off.off.solution.values,
-        1 - boiler.Q_th.submodel.on_off.on.solution.values,
+        boiler.thermal_flow.submodel.on_off.off.solution.values,
+        1 - boiler.thermal_flow.submodel.on_off.on.solution.values,
         rtol=1e-5,
         atol=1e-10,
         err_msg='"Boiler__Q_th__off" does not have the right value',
     )
     assert_allclose(
-        boiler.Q_th.submodel.flow_rate.solution.values,
+        boiler.thermal_flow.submodel.flow_rate.solution.values,
         [0, 10, 20, 0, 10],
         rtol=1e-5,
         atol=1e-10,
@@ -449,28 +449,28 @@ def test_switch_on_off(solver_fixture, time_steps_fixture):
     )
 
     assert_allclose(
-        boiler.Q_th.submodel.on_off.on.solution.values,
+        boiler.thermal_flow.submodel.on_off.on.solution.values,
         [0, 1, 1, 0, 1],
         rtol=1e-5,
         atol=1e-10,
         err_msg='"Boiler__Q_th__on" does not have the right value',
     )
     assert_allclose(
-        boiler.Q_th.submodel.on_off.switch_on.solution.values,
+        boiler.thermal_flow.submodel.on_off.switch_on.solution.values,
         [0, 1, 0, 0, 1],
         rtol=1e-5,
         atol=1e-10,
         err_msg='"Boiler__Q_th__switch_on" does not have the right value',
     )
     assert_allclose(
-        boiler.Q_th.submodel.on_off.switch_off.solution.values,
+        boiler.thermal_flow.submodel.on_off.switch_off.solution.values,
         [0, 0, 0, 1, 0],
         rtol=1e-5,
         atol=1e-10,
         err_msg='"Boiler__Q_th__switch_on" does not have the right value',
     )
     assert_allclose(
-        boiler.Q_th.submodel.flow_rate.solution.values,
+        boiler.thermal_flow.submodel.flow_rate.solution.values,
         [0, 10, 20, 0, 10],
         rtol=1e-5,
         atol=1e-10,
@@ -513,14 +513,14 @@ def test_on_total_max(solver_fixture, time_steps_fixture):
     )
 
     assert_allclose(
-        boiler.Q_th.submodel.on_off.on.solution.values,
+        boiler.thermal_flow.submodel.on_off.on.solution.values,
         [0, 0, 1, 0, 0],
         rtol=1e-5,
         atol=1e-10,
         err_msg='"Boiler__Q_th__on" does not have the right value',
     )
     assert_allclose(
-        boiler.Q_th.submodel.flow_rate.solution.values,
+        boiler.thermal_flow.submodel.flow_rate.solution.values,
         [0, 0, 20, 0, 0],
         rtol=1e-5,
         atol=1e-10,
@@ -572,14 +572,14 @@ def test_on_total_bounds(solver_fixture, time_steps_fixture):
     )
 
     assert_allclose(
-        boiler.Q_th.submodel.on_off.on.solution.values,
+        boiler.thermal_flow.submodel.on_off.on.solution.values,
         [0, 0, 1, 0, 1],
         rtol=1e-5,
         atol=1e-10,
         err_msg='"Boiler__Q_th__on" does not have the right value',
     )
     assert_allclose(
-        boiler.Q_th.submodel.flow_rate.solution.values,
+        boiler.thermal_flow.submodel.flow_rate.solution.values,
         [0, 0, 20, 0, 12 - 1e-5],
         rtol=1e-5,
         atol=1e-10,
@@ -587,14 +587,14 @@ def test_on_total_bounds(solver_fixture, time_steps_fixture):
     )
 
     assert_allclose(
-        sum(boiler_backup.Q_th.submodel.on_off.on.solution.values),
+        sum(boiler_backup.thermal_flow.submodel.on_off.on.solution.values),
         3,
         rtol=1e-5,
         atol=1e-10,
         err_msg='"Boiler_backup__Q_th__on" does not have the right value',
     )
     assert_allclose(
-        boiler_backup.Q_th.submodel.flow_rate.solution.values,
+        boiler_backup.thermal_flow.submodel.flow_rate.solution.values,
         [0, 10, 1.0e-05, 0, 1.0e-05],
         rtol=1e-5,
         atol=1e-10,
@@ -640,14 +640,14 @@ def test_consecutive_on_off(solver_fixture, time_steps_fixture):
     )
 
     assert_allclose(
-        boiler.Q_th.submodel.on_off.on.solution.values,
+        boiler.thermal_flow.submodel.on_off.on.solution.values,
         [1, 1, 0, 1, 1],
         rtol=1e-5,
         atol=1e-10,
         err_msg='"Boiler__Q_th__on" does not have the right value',
     )
     assert_allclose(
-        boiler.Q_th.submodel.flow_rate.solution.values,
+        boiler.thermal_flow.submodel.flow_rate.solution.values,
         [5, 10, 0, 18, 12],
         rtol=1e-5,
         atol=1e-10,
@@ -655,7 +655,7 @@ def test_consecutive_on_off(solver_fixture, time_steps_fixture):
     )
 
     assert_allclose(
-        boiler_backup.Q_th.submodel.flow_rate.solution.values,
+        boiler_backup.thermal_flow.submodel.flow_rate.solution.values,
         [0, 0, 20, 0, 0],
         rtol=1e-5,
         atol=1e-10,
@@ -703,21 +703,21 @@ def test_consecutive_off(solver_fixture, time_steps_fixture):
     )
 
     assert_allclose(
-        boiler_backup.Q_th.submodel.on_off.on.solution.values,
+        boiler_backup.thermal_flow.submodel.on_off.on.solution.values,
         [0, 0, 1, 0, 0],
         rtol=1e-5,
         atol=1e-10,
         err_msg='"Boiler_backup__Q_th__on" does not have the right value',
     )
     assert_allclose(
-        boiler_backup.Q_th.submodel.on_off.off.solution.values,
+        boiler_backup.thermal_flow.submodel.on_off.off.solution.values,
         [1, 1, 0, 1, 1],
         rtol=1e-5,
         atol=1e-10,
         err_msg='"Boiler_backup__Q_th__off" does not have the right value',
     )
     assert_allclose(
-        boiler_backup.Q_th.submodel.flow_rate.solution.values,
+        boiler_backup.thermal_flow.submodel.flow_rate.solution.values,
         [0, 0, 1e-5, 0, 0],
         rtol=1e-5,
         atol=1e-10,
@@ -725,7 +725,7 @@ def test_consecutive_off(solver_fixture, time_steps_fixture):
     )
 
     assert_allclose(
-        boiler.Q_th.submodel.flow_rate.solution.values,
+        boiler.thermal_flow.submodel.flow_rate.solution.values,
         [5, 0, 20 - 1e-5, 18, 12],
         rtol=1e-5,
         atol=1e-10,
diff --git a/tests/test_integration.py b/tests/test_integration.py
index 6e5da63d6..88e4a21af 100644
--- a/tests/test_integration.py
+++ b/tests/test_integration.py
@@ -37,14 +37,14 @@ def test_model_components(self, simple_flow_system, highs_solver):
 
         # Boiler assertions
         assert_almost_equal_numeric(
-            comps['Boiler'].Q_th.submodel.flow_rate.solution.values,
+            comps['Boiler'].thermal_flow.submodel.flow_rate.solution.values,
             [0, 0, 0, 28.4864, 35, 0, 0, 0, 0],
             'Q_th doesnt match expected value',
         )
 
         # CHP unit assertions
         assert_almost_equal_numeric(
-            comps['CHP_unit'].Q_th.submodel.flow_rate.solution.values,
+            comps['CHP_unit'].thermal_flow.submodel.flow_rate.solution.values,
             [30.0, 26.66666667, 75.0, 75.0, 75.0, 20.0, 20.0, 20.0, 20.0],
             'Q_th doesnt match expected value',
         )
@@ -220,7 +220,7 @@ def test_piecewise_conversion(self, flow_system_piecewise_conversion, highs_solv
             effects['CO2'].submodel.total.solution.item(), 1278.7939026086956, 'CO2 doesnt match expected value'
         )
         assert_almost_equal_numeric(
-            comps['Kessel'].Q_th.submodel.flow_rate.solution.values,
+            comps['Kessel'].thermal_flow.submodel.flow_rate.solution.values,
             [0, 0, 0, 45, 0, 0, 0, 0, 0],
             'Kessel doesnt match expected value',
         )

From 8b35f0ceff618abf41fa85d7c4f7079dc08b99bf Mon Sep 17 00:00:00 2001
From: FBumann <117816358+FBumann@users.noreply.github.com>
Date: Sun, 16 Nov 2025 17:59:33 +0100
Subject: [PATCH 17/25]  use the explicit thermal_efficiency keyword argument

---
 tests/test_functional.py | 34 +++++++++++++++++-----------------
 1 file changed, 17 insertions(+), 17 deletions(-)

diff --git a/tests/test_functional.py b/tests/test_functional.py
index 36274d494..3d76c8c81 100644
--- a/tests/test_functional.py
+++ b/tests/test_functional.py
@@ -85,7 +85,7 @@ def flow_system_minimal(timesteps) -> fx.FlowSystem:
     flow_system.add_elements(
         fx.linear_converters.Boiler(
             'Boiler',
-            0.5,
+            thermal_efficiency=0.5,
             fuel_flow=fx.Flow('Q_fu', bus='Gas'),
             thermal_flow=fx.Flow('Q_th', bus='Fernwärme'),
         )
@@ -141,7 +141,7 @@ def test_fixed_size(solver_fixture, time_steps_fixture):
     flow_system.add_elements(
         fx.linear_converters.Boiler(
             'Boiler',
-            0.5,
+            thermal_efficiency=0.5,
             fuel_flow=fx.Flow('Q_fu', bus='Gas'),
             thermal_flow=fx.Flow(
                 'Q_th',
@@ -182,7 +182,7 @@ def test_optimize_size(solver_fixture, time_steps_fixture):
     flow_system.add_elements(
         fx.linear_converters.Boiler(
             'Boiler',
-            0.5,
+            thermal_efficiency=0.5,
             fuel_flow=fx.Flow('Q_fu', bus='Gas'),
             thermal_flow=fx.Flow(
                 'Q_th',
@@ -223,7 +223,7 @@ def test_size_bounds(solver_fixture, time_steps_fixture):
     flow_system.add_elements(
         fx.linear_converters.Boiler(
             'Boiler',
-            0.5,
+            thermal_efficiency=0.5,
             fuel_flow=fx.Flow('Q_fu', bus='Gas'),
             thermal_flow=fx.Flow(
                 'Q_th',
@@ -264,7 +264,7 @@ def test_optional_invest(solver_fixture, time_steps_fixture):
     flow_system.add_elements(
         fx.linear_converters.Boiler(
             'Boiler',
-            0.5,
+            thermal_efficiency=0.5,
             fuel_flow=fx.Flow('Q_fu', bus='Gas'),
             thermal_flow=fx.Flow(
                 'Q_th',
@@ -276,7 +276,7 @@ def test_optional_invest(solver_fixture, time_steps_fixture):
         ),
         fx.linear_converters.Boiler(
             'Boiler_optional',
-            0.5,
+            thermal_efficiency=0.5,
             fuel_flow=fx.Flow('Q_fu', bus='Gas'),
             thermal_flow=fx.Flow(
                 'Q_th',
@@ -336,7 +336,7 @@ def test_on(solver_fixture, time_steps_fixture):
     flow_system.add_elements(
         fx.linear_converters.Boiler(
             'Boiler',
-            0.5,
+            thermal_efficiency=0.5,
             fuel_flow=fx.Flow('Q_fu', bus='Gas'),
             thermal_flow=fx.Flow('Q_th', bus='Fernwärme', size=100, on_off_parameters=fx.OnOffParameters()),
         )
@@ -375,7 +375,7 @@ def test_off(solver_fixture, time_steps_fixture):
     flow_system.add_elements(
         fx.linear_converters.Boiler(
             'Boiler',
-            0.5,
+            thermal_efficiency=0.5,
             fuel_flow=fx.Flow('Q_fu', bus='Gas'),
             thermal_flow=fx.Flow(
                 'Q_th',
@@ -426,7 +426,7 @@ def test_switch_on_off(solver_fixture, time_steps_fixture):
     flow_system.add_elements(
         fx.linear_converters.Boiler(
             'Boiler',
-            0.5,
+            thermal_efficiency=0.5,
             fuel_flow=fx.Flow('Q_fu', bus='Gas'),
             thermal_flow=fx.Flow(
                 'Q_th',
@@ -484,7 +484,7 @@ def test_on_total_max(solver_fixture, time_steps_fixture):
     flow_system.add_elements(
         fx.linear_converters.Boiler(
             'Boiler',
-            0.5,
+            thermal_efficiency=0.5,
             fuel_flow=fx.Flow('Q_fu', bus='Gas'),
             thermal_flow=fx.Flow(
                 'Q_th',
@@ -495,7 +495,7 @@ def test_on_total_max(solver_fixture, time_steps_fixture):
         ),
         fx.linear_converters.Boiler(
             'Boiler_backup',
-            0.2,
+            thermal_efficiency=0.2,
             fuel_flow=fx.Flow('Q_fu', bus='Gas'),
             thermal_flow=fx.Flow('Q_th', bus='Fernwärme', size=100),
         ),
@@ -534,7 +534,7 @@ def test_on_total_bounds(solver_fixture, time_steps_fixture):
     flow_system.add_elements(
         fx.linear_converters.Boiler(
             'Boiler',
-            0.5,
+            thermal_efficiency=0.5,
             fuel_flow=fx.Flow('Q_fu', bus='Gas'),
             thermal_flow=fx.Flow(
                 'Q_th',
@@ -545,7 +545,7 @@ def test_on_total_bounds(solver_fixture, time_steps_fixture):
         ),
         fx.linear_converters.Boiler(
             'Boiler_backup',
-            0.2,
+            thermal_efficiency=0.2,
             fuel_flow=fx.Flow('Q_fu', bus='Gas'),
             thermal_flow=fx.Flow(
                 'Q_th',
@@ -608,7 +608,7 @@ def test_consecutive_on_off(solver_fixture, time_steps_fixture):
     flow_system.add_elements(
         fx.linear_converters.Boiler(
             'Boiler',
-            0.5,
+            thermal_efficiency=0.5,
             fuel_flow=fx.Flow('Q_fu', bus='Gas'),
             thermal_flow=fx.Flow(
                 'Q_th',
@@ -619,7 +619,7 @@ def test_consecutive_on_off(solver_fixture, time_steps_fixture):
         ),
         fx.linear_converters.Boiler(
             'Boiler_backup',
-            0.2,
+            thermal_efficiency=0.2,
             fuel_flow=fx.Flow('Q_fu', bus='Gas'),
             thermal_flow=fx.Flow('Q_th', bus='Fernwärme', size=100),
         ),
@@ -669,13 +669,13 @@ def test_consecutive_off(solver_fixture, time_steps_fixture):
     flow_system.add_elements(
         fx.linear_converters.Boiler(
             'Boiler',
-            0.5,
+            thermal_efficiency=0.5,
             fuel_flow=fx.Flow('Q_fu', bus='Gas'),
             thermal_flow=fx.Flow('Q_th', bus='Fernwärme'),
         ),
         fx.linear_converters.Boiler(
             'Boiler_backup',
-            0.2,
+            thermal_efficiency=0.2,
             fuel_flow=fx.Flow('Q_fu', bus='Gas'),
             thermal_flow=fx.Flow(
                 'Q_th',

From ed051db00be4a855678b4c32b8267ff510e52638 Mon Sep 17 00:00:00 2001
From: FBumann <117816358+FBumann@users.noreply.github.com>
Date: Sun, 16 Nov 2025 22:24:59 +0100
Subject: [PATCH 18/25] Update test to new porperty

---
 tests/test_functional.py | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/tests/test_functional.py b/tests/test_functional.py
index 3d76c8c81..9b3c3e6d4 100644
--- a/tests/test_functional.py
+++ b/tests/test_functional.py
@@ -162,14 +162,14 @@ def test_fixed_size(solver_fixture, time_steps_fixture):
         err_msg='The total costs does not have the right value',
     )
     assert_allclose(
-        boiler.thermal_flow.submodel._investment.size.solution.item(),
+        boiler.thermal_flow.submodel.investment.size.solution.item(),
         1000,
         rtol=1e-5,
         atol=1e-10,
         err_msg='"Boiler__Q_th__Investment_size" does not have the right value',
     )
     assert_allclose(
-        boiler.thermal_flow.submodel._investment.invested.solution.item(),
+        boiler.thermal_flow.submodel.investment.invested.solution.item(),
         1,
         rtol=1e-5,
         atol=1e-10,
@@ -203,14 +203,14 @@ def test_optimize_size(solver_fixture, time_steps_fixture):
         err_msg='The total costs does not have the right value',
     )
     assert_allclose(
-        boiler.thermal_flow.submodel._investment.size.solution.item(),
+        boiler.thermal_flow.submodel.investment.size.solution.item(),
         20,
         rtol=1e-5,
         atol=1e-10,
         err_msg='"Boiler__Q_th__Investment_size" does not have the right value',
     )
     assert_allclose(
-        boiler.thermal_flow.submodel._investment.invested.solution.item(),
+        boiler.thermal_flow.submodel.investment.invested.solution.item(),
         1,
         rtol=1e-5,
         atol=1e-10,
@@ -244,14 +244,14 @@ def test_size_bounds(solver_fixture, time_steps_fixture):
         err_msg='The total costs does not have the right value',
     )
     assert_allclose(
-        boiler.thermal_flow.submodel._investment.size.solution.item(),
+        boiler.thermal_flow.submodel.investment.size.solution.item(),
         40,
         rtol=1e-5,
         atol=1e-10,
         err_msg='"Boiler__Q_th__Investment_size" does not have the right value',
     )
     assert_allclose(
-        boiler.thermal_flow.submodel._investment.invested.solution.item(),
+        boiler.thermal_flow.submodel.investment.invested.solution.item(),
         1,
         rtol=1e-5,
         atol=1e-10,
@@ -300,14 +300,14 @@ def test_optional_invest(solver_fixture, time_steps_fixture):
         err_msg='The total costs does not have the right value',
     )
     assert_allclose(
-        boiler.thermal_flow.submodel._investment.size.solution.item(),
+        boiler.thermal_flow.submodel.investment.size.solution.item(),
         40,
         rtol=1e-5,
         atol=1e-10,
         err_msg='"Boiler__Q_th__Investment_size" does not have the right value',
     )
     assert_allclose(
-        boiler.thermal_flow.submodel._investment.invested.solution.item(),
+        boiler.thermal_flow.submodel.investment.invested.solution.item(),
         1,
         rtol=1e-5,
         atol=1e-10,
@@ -315,14 +315,14 @@ def test_optional_invest(solver_fixture, time_steps_fixture):
     )
 
     assert_allclose(
-        boiler_optional.thermal_flow.submodel._investment.size.solution.item(),
+        boiler_optional.thermal_flow.submodel.investment.size.solution.item(),
         0,
         rtol=1e-5,
         atol=1e-10,
         err_msg='"Boiler__Q_th__Investment_size" does not have the right value',
     )
     assert_allclose(
-        boiler_optional.thermal_flow.submodel._investment.invested.solution.item(),
+        boiler_optional.thermal_flow.submodel.investment.invested.solution.item(),
         0,
         rtol=1e-5,
         atol=1e-10,

From 3ebfeb6a4a0273f57bccc09ca2e97eac557d7a29 Mon Sep 17 00:00:00 2001
From: FBumann <117816358+FBumann@users.noreply.github.com>
Date: Mon, 17 Nov 2025 07:51:49 +0100
Subject: [PATCH 19/25] Rename lastValueOfSim to equals_last

---
 CHANGELOG.md                                  |  4 +++
 .../two_stage_optimization.py                 |  2 +-
 flixopt/components.py                         | 26 ++++++++++++-------
 tests/test_scenarios.py                       |  2 +-
 tests/test_storage.py                         |  2 +-
 5 files changed, 23 insertions(+), 13 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a3ccfc968..3a6af2e8f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -74,6 +74,9 @@ If upgrading from v2.x, see the [v3.0.0 release notes](https://github.com/flixOp
         - `CHP`: `eta_th` → `thermal_efficiency`, `eta_el` → `electrical_efficiency`
         - `HetaPump`: `COP` → `cop`
         - `HetaPumpWithSource`: `COP` → `cop`
+    - **Storage Parameters**:
+        - `initial_charge_state="lastValueOfSim"` -> `initial_charge_state="equals_last"`
+
 
 
 ### 🗑️ Deprecated
@@ -81,6 +84,7 @@ If upgrading from v2.x, see the [v3.0.0 release notes](https://github.com/flixOp
     - **Flow parameters**: `Q_fu`, `Q_th`, `P_el`, `Q_ab`, `power_flow` (use `fuel_flow`, `thermal_flow`, `electrical_flow`, `heat_source_flow` instead)
     - **Efficiency parameters**: `eta`, `eta_th`, `eta_el` (use `thermal_efficiency`, `electrical_efficiency` instead)
     - **COP parameter**: `COP` (use lowercase `cop` instead)
+    - **Storage Parameter**: 'initial_charge_state'="lastValueOfSim" (use ="equals_last")
 
 ### 🔥 Removed
 
diff --git a/examples/05_Two-stage-optimization/two_stage_optimization.py b/examples/05_Two-stage-optimization/two_stage_optimization.py
index 39a3aea0b..6c7b20276 100644
--- a/examples/05_Two-stage-optimization/two_stage_optimization.py
+++ b/examples/05_Two-stage-optimization/two_stage_optimization.py
@@ -82,7 +82,7 @@
             capacity_in_flow_hours=fx.InvestParameters(
                 minimum_size=10, maximum_size=1000, effects_of_investment_per_size={'costs': 60}
             ),
-            initial_charge_state='lastValueOfSim',
+            initial_charge_state='equals_final',
             eta_charge=1,
             eta_discharge=1,
             relative_loss_per_hour=0.001,
diff --git a/flixopt/components.py b/flixopt/components.py
index c51b4b7d2..83b47d09c 100644
--- a/flixopt/components.py
+++ b/flixopt/components.py
@@ -275,7 +275,7 @@ class Storage(Component):
             Scalar for fixed size or InvestParameters for optimization.
         relative_minimum_charge_state: Minimum charge state (0-1). Default: 0.
         relative_maximum_charge_state: Maximum charge state (0-1). Default: 1.
-        initial_charge_state: Charge at start. Numeric or 'lastValueOfSim'. Default: 0.
+        initial_charge_state: Charge at start. Numeric or 'equals_final'. Default: 0.
         minimal_final_charge_state: Minimum absolute charge required at end (optional).
         maximal_final_charge_state: Maximum absolute charge allowed at end (optional).
         relative_minimum_final_charge_state: Minimum relative charge at end.
@@ -339,7 +339,7 @@ class Storage(Component):
             ),
             eta_charge=0.85,  # Pumping efficiency
             eta_discharge=0.90,  # Turbine efficiency
-            initial_charge_state='lastValueOfSim',  # Ensuring no deficit compared to start
+            initial_charge_state='equals_final',  # Ensuring no deficit compared to start
             relative_loss_per_hour=0.0001,  # Minimal evaporation
         )
         ```
@@ -388,7 +388,7 @@ def __init__(
         capacity_in_flow_hours: Numeric_PS | InvestParameters,
         relative_minimum_charge_state: Numeric_TPS = 0,
         relative_maximum_charge_state: Numeric_TPS = 1,
-        initial_charge_state: Numeric_PS | Literal['lastValueOfSim'] = 0,
+        initial_charge_state: Numeric_PS | Literal['equals_final'] = 0,
         minimal_final_charge_state: Numeric_PS | None = None,
         maximal_final_charge_state: Numeric_PS | None = None,
         relative_minimum_final_charge_state: Numeric_PS | None = None,
@@ -408,6 +408,13 @@ def __init__(
             prevent_simultaneous_flows=[charging, discharging] if prevent_simultaneous_charge_and_discharge else None,
             meta_data=meta_data,
         )
+        if isinstance(initial_charge_state, str) and initial_charge_state == 'lastValusOfSim':
+            warnings.warn(
+                f'{initial_charge_state=} is deprecated. Use "equals_final" instead.',
+                DeprecationWarning,
+                stacklevel=2,
+            )
+            initial_charge_state = 'equals_final'
 
         self.charging = charging
         self.discharging = discharging
@@ -483,12 +490,11 @@ def _plausibility_checks(self) -> None:
         super()._plausibility_checks()
 
         # Validate string values and set flag
-        initial_is_last = False
+        initial_equals_final = False
         if isinstance(self.initial_charge_state, str):
-            if self.initial_charge_state == 'lastValueOfSim':
-                initial_is_last = True
-            else:
-                raise PlausibilityError(f'initial_charge_state has undefined value: {self.initial_charge_state}')
+            if not self.initial_charge_state == 'equals_final':
+                raise PlausibilityError(f'equals_finalcharge_state has undefined value: {self.initial_charge_state}')
+            initial_equals_final = True
 
         # Use new InvestParameters methods to get capacity bounds
         if isinstance(self.capacity_in_flow_hours, InvestParameters):
@@ -502,8 +508,8 @@ def _plausibility_checks(self) -> None:
         minimum_initial_capacity = maximum_capacity * self.relative_minimum_charge_state.isel(time=0)
         maximum_initial_capacity = minimum_capacity * self.relative_maximum_charge_state.isel(time=0)
 
-        # Only perform numeric comparisons if not using 'lastValueOfSim'
-        if not initial_is_last:
+        # Only perform numeric comparisons if not using 'equals_final'
+        if not initial_equals_final:
             if (self.initial_charge_state > maximum_initial_capacity).any():
                 raise PlausibilityError(
                     f'{self.label_full}: {self.initial_charge_state=} '
diff --git a/tests/test_scenarios.py b/tests/test_scenarios.py
index c25750259..f63405641 100644
--- a/tests/test_scenarios.py
+++ b/tests/test_scenarios.py
@@ -85,7 +85,7 @@ def test_system():
         ),
         eta_charge=0.95,
         eta_discharge=0.95,
-        initial_charge_state='lastValueOfSim',
+        initial_charge_state='equals_final',
     )
 
     # Create effects and objective
diff --git a/tests/test_storage.py b/tests/test_storage.py
index 8d0c495c2..6220ee08a 100644
--- a/tests/test_storage.py
+++ b/tests/test_storage.py
@@ -362,7 +362,7 @@ def test_storage_cyclic_initialization(self, basic_flow_system_linopy_coords, co
             charging=fx.Flow('Q_th_in', bus='Fernwärme', size=20),
             discharging=fx.Flow('Q_th_out', bus='Fernwärme', size=20),
             capacity_in_flow_hours=30,
-            initial_charge_state='lastValueOfSim',  # Cyclic initialization
+            initial_charge_state='equals_final',  # Cyclic initialization
             eta_charge=0.9,
             eta_discharge=0.9,
             relative_loss_per_hour=0.05,

From 33e227816576e17d6c2fa48c4929e7299cb94acd Mon Sep 17 00:00:00 2001
From: FBumann <117816358+FBumann@users.noreply.github.com>
Date: Mon, 17 Nov 2025 07:53:17 +0100
Subject: [PATCH 20/25] Remove white space

---
 CHANGELOG.md | 2 --
 1 file changed, 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3a6af2e8f..b33cdfd3a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -77,8 +77,6 @@ If upgrading from v2.x, see the [v3.0.0 release notes](https://github.com/flixOp
     - **Storage Parameters**:
         - `initial_charge_state="lastValueOfSim"` -> `initial_charge_state="equals_last"`
 
-
-
 ### 🗑️ Deprecated
 - **Old parameter names in `linear_converters.py`**: The following parameter names are now deprecated and accessible as properties/kwargs that emit `DeprecationWarning`. They will be removed in v4.0.0:
     - **Flow parameters**: `Q_fu`, `Q_th`, `P_el`, `Q_ab`, `power_flow` (use `fuel_flow`, `thermal_flow`, `electrical_flow`, `heat_source_flow` instead)

From 34543fc84c6b10e39c3850a3584bfb54e9494d7b Mon Sep 17 00:00:00 2001
From: FBumann <117816358+FBumann@users.noreply.github.com>
Date: Mon, 17 Nov 2025 08:01:24 +0100
Subject: [PATCH 21/25] Fix CHANGELOG.md

---
 CHANGELOG.md | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a3ccfc968..5bb134d52 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -63,11 +63,11 @@ If upgrading from v2.x, see the [v3.0.0 release notes](https://github.com/flixOp
 - **Parameter renaming in `linear_converters.py`**: Renamed parameters to use lowercase, descriptive names for better consistency and clarity:
     - **Flow parameters** (deprecated uppercase abbreviations → descriptive names):
         - `Boiler`: `Q_fu` → `fuel_flow`, `Q_th` → `thermal_flow`
-        - `Power2Heat`: `P_el` → `power_flow` → `electrical_flow`, `Q_th` → `thermal_flow`
-        - `HeatPump`: `COP` → `cop`, `P_el` → `power_flow` → `electrical_flow`, `Q_th` → `thermal_flow`
-        - `CoolingTower`: `P_el` → `power_flow` → `electrical_flow`, `Q_th` → `thermal_flow`
-        - `CHP`: `Q_fu` → `fuel_flow`, `P_el` → `power_flow` → `electrical_flow`, `Q_th` → `thermal_flow`
-        - `HeatPumpWithSource`: `COP` → `cop`, `P_el` → `power_flow` → `electrical_flow`, `Q_ab` → `heat_source_flow`, `Q_th` → `thermal_flow`
+        - `Power2Heat`: `P_el` → `electrical_flow`, `Q_th` → `thermal_flow`
+        - `HeatPump`: `COP` → `cop`, `P_el` → `electrical_flow`, `Q_th` → `thermal_flow`
+        - `CoolingTower`: `P_el` → `electrical_flow`, `Q_th` → `thermal_flow`
+        - `CHP`: `Q_fu` → `fuel_flow`, `P_el` → `electrical_flow`, `Q_th` → `thermal_flow`
+        - `HeatPumpWithSource`: `COP` → `cop`, `P_el` → `electrical_flow`, `Q_ab` → `heat_source_flow`, `Q_th` → `thermal_flow`
     - **Efficiency parameters** (abbreviated → descriptive names):
         - `Boiler`: `eta` → `thermal_efficiency`
         - `Power2Heat`: `eta` → `thermal_efficiency`
@@ -78,7 +78,7 @@ If upgrading from v2.x, see the [v3.0.0 release notes](https://github.com/flixOp
 
 ### 🗑️ Deprecated
 - **Old parameter names in `linear_converters.py`**: The following parameter names are now deprecated and accessible as properties/kwargs that emit `DeprecationWarning`. They will be removed in v4.0.0:
-    - **Flow parameters**: `Q_fu`, `Q_th`, `P_el`, `Q_ab`, `power_flow` (use `fuel_flow`, `thermal_flow`, `electrical_flow`, `heat_source_flow` instead)
+    - **Flow parameters**: `Q_fu`, `Q_th`, `P_el`, `Q_ab`  (use `fuel_flow`, `thermal_flow`, `electrical_flow`, `heat_source_flow` instead)
     - **Efficiency parameters**: `eta`, `eta_th`, `eta_el` (use `thermal_efficiency`, `electrical_efficiency` instead)
     - **COP parameter**: `COP` (use lowercase `cop` instead)
 

From 71c2c7e79eb9c29cee74b960d74516854a9b3f82 Mon Sep 17 00:00:00 2001
From: FBumann <117816358+FBumann@users.noreply.github.com>
Date: Mon, 17 Nov 2025 08:48:49 +0100
Subject: [PATCH 22/25] Typo

---
 flixopt/components.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/flixopt/components.py b/flixopt/components.py
index 83b47d09c..c5b3b496d 100644
--- a/flixopt/components.py
+++ b/flixopt/components.py
@@ -493,7 +493,7 @@ def _plausibility_checks(self) -> None:
         initial_equals_final = False
         if isinstance(self.initial_charge_state, str):
             if not self.initial_charge_state == 'equals_final':
-                raise PlausibilityError(f'equals_finalcharge_state has undefined value: {self.initial_charge_state}')
+                raise PlausibilityError(f'initial_charge_state has undefined value: {self.initial_charge_state}')
             initial_equals_final = True
 
         # Use new InvestParameters methods to get capacity bounds

From 809f20bf52d9243965072eff08a4ba39920380fc Mon Sep 17 00:00:00 2001
From: FBumann <117816358+FBumann@users.noreply.github.com>
Date: Mon, 17 Nov 2025 17:26:43 +0100
Subject: [PATCH 23/25] Typo

---
 flixopt/components.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/flixopt/components.py b/flixopt/components.py
index c5b3b496d..0de9cf982 100644
--- a/flixopt/components.py
+++ b/flixopt/components.py
@@ -408,7 +408,7 @@ def __init__(
             prevent_simultaneous_flows=[charging, discharging] if prevent_simultaneous_charge_and_discharge else None,
             meta_data=meta_data,
         )
-        if isinstance(initial_charge_state, str) and initial_charge_state == 'lastValusOfSim':
+        if isinstance(initial_charge_state, str) and initial_charge_state == 'lastValueOfSim':
             warnings.warn(
                 f'{initial_charge_state=} is deprecated. Use "equals_final" instead.',
                 DeprecationWarning,

From 7cf22f228c544c91f7c4ce06fadf27590bfcf431 Mon Sep 17 00:00:00 2001
From: FBumann <117816358+FBumann@users.noreply.github.com>
Date: Mon, 17 Nov 2025 17:28:39 +0100
Subject: [PATCH 24/25] Improve CHANGELOG.md

---
 CHANGELOG.md | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index ba53e1a09..fd85e9249 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -75,19 +75,19 @@ If upgrading from v2.x, see the [v3.0.0 release notes](https://github.com/flixOp
         - `HetaPump`: `COP` → `cop`
         - `HetaPumpWithSource`: `COP` → `cop`
     - **Storage Parameters**:
-        - `initial_charge_state="lastValueOfSim"` -> `initial_charge_state="equals_last"`
+        - `Storage`: `initial_charge_state="lastValueOfSim"` → `initial_charge_state="equals_last"`
 
 ### 🗑️ Deprecated
 - **Old parameter names in `linear_converters.py`**: The following parameter names are now deprecated and accessible as properties/kwargs that emit `DeprecationWarning`. They will be removed in v4.0.0:
     - **Flow parameters**: `Q_fu`, `Q_th`, `P_el`, `Q_ab`  (use `fuel_flow`, `thermal_flow`, `electrical_flow`, `heat_source_flow` instead)
     - **Efficiency parameters**: `eta`, `eta_th`, `eta_el` (use `thermal_efficiency`, `electrical_efficiency` instead)
     - **COP parameter**: `COP` (use lowercase `cop` instead)
-    - **Storage Parameter**: 'initial_charge_state'="lastValueOfSim" (use ="equals_last")
+    - **Storage Parameter**: `Storage`: `initial_charge_state="lastValueOfSim"` (use `initial_charge_state="equals_last"`)
 
 ### 🔥 Removed
 
 ### 🐛 Fixed
-- Fixed `check_bounds` function in `linear_converters.py` to use normalized array for comparisons, improving robustness with array-like inputs
+- Fixed `check_bounds` function in `linear_converters.py` to normalize array inputs before comparisons, ensuring correct boundary checks with DataFrames, Series, and other array-like types
 
 ### 🔒 Security
 

From 2373dea52d466ea0c40448eeb052d68699c58db2 Mon Sep 17 00:00:00 2001
From: FBumann <117816358+FBumann@users.noreply.github.com>
Date: Tue, 18 Nov 2025 19:17:58 +0100
Subject: [PATCH 25/25] Update Changelog

---
 CHANGELOG.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5b42834cf..82a98ea85 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -51,7 +51,7 @@ If upgrading from v2.x, see the [v3.0.0 release notes](https://github.com/flixOp
 
 ## [Unreleased] - ????-??-??
 
-**Summary**: Renaming parameters in Linear Transformers for readability & Internal architecture improvements to simplify FlowSystem-Element coupling and eliminate circular dependencies.
+**Summary**: Renaming parameters in Linear Transformers for readability & Internal architecture improvements to simplify FlowSystem-Element coupling and eliminate circular dependencies. Old parameters till work but emmit warnings.
 
 If upgrading from v2.x, see the [v3.0.0 release notes](https://github.com/flixOpt/flixOpt/releases/tag/v3.0.0) and [Migration Guide](https://flixopt.github.io/flixopt/latest/user-guide/migration-guide-v3/).