How much does it cost to run a heat pump?

An air source heat pump delivers more heat than the electricity it uses. Running cost = annual heat demand ÷ seasonal coefficient of performance (SCOP) × your electricity price. The defaults are a typical three-bedroom semi and a well-designed installation; change them to your survey figures.

Where to find the numbers

Annual heat demand (space heating plus hot water) is on your MCS heat loss calculation or your heat pump quote; the previous year’s gas use in kWh × 0.85 is a rough stand-in. SCOP is on the heat pump’s data sheet and the MCS certificate. Your electricity price is the unit rate on your bill, or your heat pump tariff rate.

What the figure is based on

SCOP depends on flow temperature: a system designed for 35–45 °C radiators runs at 3.5–4.5; one pushed to 55 °C or more can drop below 3. Hot water and defrost cycles pull the real figure down. This is electricity only; standing charges and servicing are not included.

What changes the cost

• Flow temperature: radiators run at 35–45 °C give a SCOP of 3.5–4.5; pushing to 55 °C or more can drop it below 3.
• Insulation and heat loss: the heat demand figure is set by the house, not the heat pump.
• Hot water: cylinder heating runs at a higher temperature and lower efficiency than space heating.
• Weather compensation and steady running beat on-off timer schedules for a heat pump.
• Tariff: heat pump and off-peak tariffs change the price per kWh more than any setting change.

For a specific model or any other appliance, use the electricity cost calculator.