What you need to know
- COP links delivered heat to electrical input at a specific operating point.
- Outdoor temperature and flow temperature can change performance.
- Use seasonal data or measured consumption when you need a better annual estimate.
Use your own measurements
Use the linked BricoDato resource to check these inputs in your own situation. A heat pump moves heat; its thermal output is not the same as its electrical input.
Start with heat demand
If the home needs 3 kW of heat and the heat pump operates at COP 3, electrical input is about 1 kW at that moment.
COP is not constant
Efficiency changes with outdoor temperature, indoor setpoint, defrost cycles and the temperature the system must deliver.
COP and SCOP are different
COP describes a particular test condition. SCOP is intended to represent seasonal performance and is more useful for broad annual comparisons.
Measure when possible
Smart-meter or dedicated energy data over several days can reveal cycling, weather effects and whether assumptions match reality.
A heat-pump COP calculation with limits
A heat pump moves heat; its thermal output is not the same as its electrical input. COP is measured under specified conditions and can fall as outside temperature and operating requirements change.
Example to adapt
If a heat pump delivers an illustrative 6 kW of heat at COP 3, input is 6 ÷ 3 = 2 kW while that condition holds. For 5 equivalent full-load hours, the estimate is 10 kWh. At €0.20/kWh, the energy-only cost is €2.00. At COP 2, the same delivered heat would require 3 kW or 15 kWh over five hours.
| Operating COP | Input for 6 kW heat | Energy for 5 h |
|---|---|---|
| 2 | 3.0 kW | 15 kWh |
| 3 | 2.0 kW | 10 kWh |
| 4 | 1.5 kW | 7.5 kWh |
Checks before acting
- Use actual heat demand rather than installed maximum output for long-term estimates.
- Distinguish an instantaneous COP from seasonal SCOP figures and test conditions.
- Consider defrost, auxiliary electric heating and hot-water settings separately.
- Measure across representative colder and milder days if comparing real running costs.
Final check
Keep useful heating output and electrical energy separate. If a room needs 1,200 kWh of delivered heat during a period and a system averages a hypothetical seasonal efficiency of 3, electricity consumption is around 1,200 ÷ 3 = 400 kWh. The manufacturer’s ideal-condition COP is not that seasonal figure; outdoor temperatures, defrost and airflow can change the achieved result.
- Use realistic heat demand.
- Do not assume one COP all year.
- Compare similar weather and setpoints.
- Separate space heating from hot-water use when possible.
Keep a small job sheet
Keep outdoor temperature, heat output estimate, COP assumption, run time and metered kWh.
Turn the guide into a decision
Build estimates from heat demand, local weather and a realistic SCOP for the exact installation. Compare comfort and kWh across comparable weeks, and consult a qualified installer if sizing, refrigerant, electrical supply or drainage must change.