COP (Coefficient of Performance) is the ratio of useful heat a heat pump delivers to the electricity it consumes at one fixed test condition. A COP of 4.0 means 1 kWh of electricity produces 4 kWh of heat. Modern air-to-water heat pumps typically achieve a COP between 3.0 and 5.0.
How is COP calculated?
COP is calculated by dividing heat output by electrical input, both measured in kilowatts under laboratory conditions defined in EN 14511. A heat pump delivering 8 kW of heat while drawing 2 kW of electricity operates at a COP of 4.0.
The test condition is always written next to the value. A7/W35 means 7 °C outdoor air and 35 °C water outlet — the standard rating point for air-to-water heat pumps. The same machine tested at A2/W55 (colder air, hotter water) will show a much lower COP, which is why two datasheets can only be compared at the same test point.
What is a good COP for a heat pump?
| Test point | Typical modern air/water heat pump | Interpretation |
|---|---|---|
| A7/W35 | 4.0 – 5.0 | Standard rating point |
| A2/W35 | 3.2 – 4.2 | Cold-weather performance |
| A-7/W35 | 2.5 – 3.3 | Design condition in cold climates |
| A7/W55 | 2.8 – 3.5 | High-temperature radiators / DHW |
As a rule of thumb, every degree you lower the flow temperature improves efficiency by roughly 2–3%. This is why heat pumps pair so well with underfloor heating and properly sized buffer tanks.
COP vs SCOP: what is the difference?
COP is a snapshot at one condition; SCOP (Seasonal Coefficient of Performance) averages performance across a full heating season using the EN 14825 climate profile. SCOP is the number European energy labels and most subsidy schemes use — for example, Germany's BEG funding requires heat pumps to reach a seasonal efficiency equivalent to SCOP ≥ 3.0. See SCOP for details.
Why COP matters for running costs
At a COP of 4.0, heat costs roughly a quarter of what direct electric heating costs. Combined with a PVT or photovoltaic system supplying part of the electricity, the effective cost per kWh of heat drops further — the basis of most solar-plus-heat-pump system designs.
Frequently asked questions
Can a COP be higher than the theoretical maximum?
No. The theoretical ceiling (Carnot limit) depends on the temperature difference between source and output. Real heat pumps reach roughly 40–55% of the Carnot limit; a datasheet COP far above competitors at the same test point deserves scepticism.
Does COP include the backup electric heater?
No. COP is measured for the refrigerant circuit at a fixed condition. Seasonal metrics like SCOP account for backup heater use across the season, which is one reason SCOP is lower than the best-point COP.
What COP do Solimpeks heat pumps achieve?
Solimpeks air-to-water heat pumps achieve COP values up to 4.92 at A7/W35 (Varm Up Series), with EVI compressor models operating down to -30 °C. Model-specific COP tables are published on each product page.