COP (coefficient of performance)
The COP indicates how much heat a heat pump generates from one kilowatt-hour of electricity: measured on a test bench, at a single operating point.
- Evaporator: the cold refrigerant absorbs heat from the air, ground or water and evaporates.
- Compressor: it compresses the vapour, which increases the temperature. Electricity is needed here.
- Condenser: the hot vapour releases its heat to the heating water and becomes liquid again.
- Expansion valve: the pressure drops, the refrigerant cools down, and the cycle starts all over again.
COP stands for 'Coefficient of Performance'. It describes the ratio of heat output delivered to the electrical power input. A COP of 4.5 means: at that moment, 1 kW of electricity is converted into 4.5 kW of heat.
The catch: only one operating point
The COP is determined on a test bench under specified conditions. The designation reveals which ones: A7/W35 means outdoor air at 7 °C and heating water at 35 °C, B0/W35 stands for brine (geothermal) at 0 °C, and W10/W35 for groundwater at 10 °C. klimaaktiv compares the COP to the standard fuel consumption of a car on a test bench. What your system actually achieves over a whole year is only shown by the seasonal performance factor (JAZ). The two values can differ significantly.
Guide values
The klimaaktiv Wegweiser (klimaaktiv Guide) specifies recommended minimum values, which must be verified by a performance test according to EN 14511 by an accredited testing institute:
- Air: COP A7/W35 over 4.5
- Ground: COP B0/W35 over 4.5
- Groundwater: COP W10/W35 over 5.5
How to use the COP
Only compare COP values under identical test conditions. A value at A7/W35 tells you nothing about how the appliance operates at -10 °C and a 55 °C flow temperature. Ask in the quote for the calculated seasonal performance factor (JAZ) for your house. You can find help with checking this under Checking the quote.
Related terms
Seasonal performance factor (JAZ)SCOP (seasonal coefficient of performance)Flow temperatureEfficiency class (ErP energy label)
Sources
- klimaaktiv: So läuft Ihre Wärmepumpe rund. Tipps für die Planung und Installation (klimaaktiv: How to Keep Your Heat Pump Running Smoothly. Tips for Planning and Installation, BMK, 2024) (accessed on 4 October 2026)
- klimaaktiv Wegweiser zur guten Installation von Wärmepumpen (klimaaktiv Guide to Good Installation of Heat Pumps, BMK, 2020) (accessed on 4 October 2026)