Heat pump running cost for a 4-bedroom detached house
A 4-bedroom detached house uses roughly 19,250 kWh of heat a year. At the current Ofgem price cap an air source heat pump (SCOP 3.5) would cost about £1,436/yr to run, versus about £1,674/yr for mains gas. That is roughly £238 saved a year. A typical ~10kW system costs about £14,000, or £6,500 after the £7,500 grant, paying back in about 27.3 years.
Your standard rate. The tariff scenario is shown separately.
Efficiency. 3.5 is typical.
On a standard tariff (price cap)
electricity at 26.11p/kWh
£238 /yr saved
Heat pump £1,436/yr · payback 27.3 yrs
On a heat pump tariff (~15p/kWh)
cheap-rate electricity
£849 /yr saved
Heat pump £825/yr · payback 7.7 yrs
Heat pump tariffs (Octopus Cosy, EDF, Scottish Power) offered off-peak rates of about 14p to 15p/kWh in June 2026. The ~15p scenario assumes most heating runs in the cheap hours.
- Now: mains gas heating
- £1,674/yr
- Gas standing charge saved
- £106/yr
- Indicative system size
- ~10kW
- Install after grant
- £6,500
- CO₂ saved
- 2,776 kg/yr
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Estimate only. Real figures depend on your home, install and tariff. Prices: Ofgem cap, Jul-Sep 2026.