Heat Pump
A heat pump is a device that uses work to transport environmental heat into heat at a useful temperature level. In our model, we have electric heat pumps available as a technology.
The heat pump technology models a small to medium size heat pump located in a building.
The power available to the heating system is given by the electric input power multiplied with the coefficient of performance (COP). ..math:: P_\text{out} = \text{COP} \cdot P_\text{elec}
Our model contains a module for the detailed modeling of the COP based on properties of the building and the heat pumps. For this, there are plenty of parameters in the input file.
Attribute |
Unit |
Data type |
Description |
deployment |
– |
bool |
If set to ‘true’, the technology will be considered in the energy system model (this does not necessarily mean it will be used). Only relevant for optimisation. |
kW_th_max |
kW |
str |
Maximum thermal capacity (i.e. heat output). |
co2_intensity |
kg CO2/kWh |
float |
Carbon-dioxide intensity of technology output (annual average value). |
lifetime |
years |
int |
Expected lifetime of technology before replacement is required. |
interest_rate |
– |
float |
Interest rate for computing levelised costs (if required). |
capex |
CHF/kWp |
float |
CAPEX cost of technology per unit of capacity (new installations). |
capex_one_to_one_replacement |
CHF/kWp |
float |
CAPEX cost of technology per unit of capacity (when device has reached the end of life). |
maintenance_cost |
CHF/kWp/year |
float |
OPEX cost of technology. |
fixed_demand_share |
bool |
||
fixed_demand_share_val |
float |
||
only_allow_existing |
– |
bool |
If True, only existing heat pumps are allowed to continue to operate. |
cop_mode |
– |
str |
Method for estimating the COP timeseries. Options are: “from_file”, “constant”, “from_file_adjusted_to_spf”, “location_based”. “location_based” is an intricate algorithm taking into account building and heat pump properties as well as the local weather (detailed description below). “constant” means that a constant COP is used. “from_file” means means that a timeseries loaded from a given file is used. “from_file_adjusted_to_spf” means that a timeseries loaded form a file is is scaled s.t. a given value for the seasonal performance factor (SPF) is reached |
cop_timeseries_file_path |
<path> |
str |
Path to COP timeseries file for mode “form_file” and “from_file_adjusted_to_spf” |
cop_constant_value |
– |
float |
Constant COP value to use if cop_mode=constant |
spf_to_target |
– |
float |
Seasonal performance factor (SPF) to which the COP is adjusted in the mode from_file_adjusted_spf |
quality_factor_ashp_new |
– |
float |
Quality factor for new ASHPs for mode “location_based”. |
quality_factor_ashp_old |
– |
float |
Quality factor for old ASHPs for mode “location_based”. |
quality_factor_gshp_new |
– |
float |
Quality factor for new GSHPs for mode “location_based”. |
quality_factor_gshp_old |
– |
float |
Quality factor for old GSHPs for mode “location_based”. |
Name |
Standard value |
Description |
|---|---|---|
deployment |
True |
Are heat pumps deployed in the energy system? |
kW_th_max |
‘inf’ |
Maximum power of the heat pumps |
co2_intensity |
0 |
CO2 intensity of heat pumps (per kWh heat produced). CO2 for electricity used is already accounted for via electricity import CO2 intensity. |
lifetime |
25 |
Lifetime of the heat pumps. (in years) |
interest_rate |
global variable |
Interest rate used for cost calculation. Usually a global variable (the same for all technologies.) |
capex |
6000 |
Capex for building new heat pumps (per kW) CHF/kW |
capex_one_to_one_replacement |
2000 |
Capex for replacing a heat pump by a new heat pump CHF/kW. (i.e. only replacing the heat pump by a newer one) |
maintenance_cost |
10 |
Maintenance cost of the heat pump CHF/kW/year |
fixed_demand_share |
False |
|
fixed_demand_share_val |
0.0 |
|
only_allow_existing |
False |
If True, only existing heat pumps are allowed to continue to operate. |
cop_mode |
“location_based” |
Method for estimating the COP timeseries. Options are: “from_file”, “constant”, “from_file_adjusted_to_spf”, “location_based”. “location_based” is an intricate algorithm taking into account building and heat pump properties as well as the local weather (detailed description below). “constant” means that a constant COP is used. “from_file” means means that a timeseries loaded from a given file is used. “from_file_adjusted_to_spf” means that a timeseries loaded form a file is is scaled s.t. a given value for the seasonal performance factor (SPF) is reached |
cop_timeseries_file_path |
“” |
Path to COP timeseries file for mode “form_file” and “from_file_adjusted_to_spf” |
cop_constant_value |
3.0 |
Constant COP value for COP mode “constant” |
spf_to_target |
4.0 |
SPF for COP mode “from_file_adjusted_to_spf” |
quality_factor_ashp_new |
0.4 |
Quality factor for new ASHPs for mode “location_based”. |
quality_factor_ashp_old |
0.4 |
Quality factor for old ASHPs for mode “location_based”. |
quality_factor_gshp_new |
0.48 |
Quality factor for new GSHPs for mode “location_based”. |
quality_factor_gshp_old |
0.48 |
Quality factor for old GSHPs for mode “location_based”. |
COP modes
There are several ways to set the COP of the heat pumps.
In the mode “constant”, a constant, user-defined COP is used.
In the mode “from_file”, a timeseries provided by the user as file is used.
In the mode “from_file_adjusted_to_spf”, a timeseries provided by the user is used but using the demand profile, it is scaled such that the SPF reaches a user-defined value.
In the mode “location_based”, a COP model taking into account many properties of the building stock and location is used. This model is described further below.
“location_based” COP mode
The “location_based” COP mode is the standard COP mode. It calculates a COP timeseries based on the properties of the individual buildings, the quality_factors specified in the input file, the local weather and internal parameters defined in the corresponding code file.
For each building, the algorithm assign probabilities for several properties for space heating
Is the heat dissipator radiator- or underfloor-heating-based
Is the heat pump air-source or ground-source.
Does the heat pump already exist or is it a new device to be installed by the optimizer.
Which heating curve construction period is used.
and for domestic hot water-heating
Is the heat pump air-source or ground-source.
Does the heat pump already exist or is it a new device to be installed by the optimizer.
For each building, we assign a construction year. This year is the GBAUJ from the RBD if it is defined. Otherwise, the construction period (GBAUP) is used and the central year of the construction period is assigned as construction year.
The share of radiators is assumed to be 100% until 1970. From then on, it rises by 1.66% per year until reaching 100% in 2030. The year here is the construction year of the building.
The share of ASHPs is assumed to be 66% for existing installations (34% GSHP), while for new installations, 72% ASHPs and 28% GSHPs is assumed. These percentages are based on the statistics for sold heat pumps by the FWS (FWS, 2025). For existing installations, this is only used if the heat source is not specified in the RBD.
Whether the heat pump already exists is based on the RBD-information (FSO, 2025).
For the definition of the heating curve construction period, we rely on the information sheet “Heizkurve richtig einstellen” by the Swiss Federal Office of Energy (SwissEnergy, 2022).
For air-source heat pumps, the outdoor temperature is used as source temperature. For ground-source heat pumps, a simple harmonic function is used as source temperature, with a mean value of 5°C and an amplitude of 3°C, where the lowest point is reached at the end of February.
For the domestic hot water, a constant temperature of 55°C is assumed.
The COP is then calculated based on the Carnot efficiency of a perfect heat pump, capping the efficiency at 20. This value is then corrected by the quality_factor provided by the user.
where temperatures are in kelvin and refer to the condenser (output) and evaporator (source) sides of the heat pump.
This efficiency is then different for newly installed HPs than for the existing ones. Usually the existing HPs profit from being in more modern buildings, which yields lower heating water temperatures and thereby higher efficiencies, but their efficiency is reduced by the age of the existing heat pumps, which have lower device-level efficiencies, and by the fact that new buildings have a higher share of DHW, which is hotter than heating water.
References
SwissEnergy (2022, August 29). Set the heating curve correctly Federal Office of Energy. https://pubdb.bfe.admin.ch/en/publication/download/9982
FWS (2025). Jahres-Statistiken & Marktzahlen FWS Fachvereinigung Wärmepumpen Schweiz. https://www.fws.ch/statistiken/
Federal Statistical Office (FSO). (2025). Federal register of buildings and dwellings (RBD). https://www.bfs.admin.ch/bfs/en/home/registers/federal-register-buildings-dwellings.html