running costsair source heat pumpUK
Air source heat pump running costs UK: realistic numbers for 2025
Published 1 May 2025
One of the first questions homeowners ask about heat pumps is: what will it cost to run?
The honest answer depends on four things: your home's heat loss, the heat pump's efficiency (COP), the electricity price you pay, and how well the system is set up.
What drives your heat pump running cost?
A heat pump uses electricity to move heat from outside air into your home. Its efficiency is expressed as the Coefficient of Performance (COP) — the ratio of heat output to electricity input. A COP of 3.5 means the pump produces 3.5 kWh of heat for every 1 kWh of electricity it uses.
Your annual running cost is: Annual heat demand (kWh) ÷ average COP × electricity price (p/kWh)
Typical annual costs (2025 prices, ~28p/kWh electricity)
| Home | Heat demand | SCOP | Annual cost |
|---|---|---|---|
| 2-bed flat | 7,000 kWh | 3.8 | ~£515 |
| 3-bed semi | 12,000 kWh | 3.5 | ~£960 |
| 4-bed detached | 17,000 kWh | 3.2 | ~£1,487 |
How to reduce your running costs
- Switch to a heat pump tariff — Octopus Cosy, Agile, and Economy 7 offer off-peak electricity as cheap as 7–15p/kWh
- Set a sensible flow temperature — Reducing from 55–60 °C to 35–45 °C significantly improves COP
- Keep the outdoor unit clear — Restricted airflow reduces efficiency
- Do not turn your heat pump off at night — Set a setback temperature (e.g. 16 °C) rather than switching off entirely