Heat pump running cost for a 4-bedroom flat / apartment
A 4-bedroom flat / apartment uses roughly 12,000 kWh of heat a year. At the current Ofgem price cap an air source heat pump (SCOP 3.5) would cost about £895/yr to run, versus about £1,083/yr for mains gas. That is roughly £188 saved a year. A typical ~6kW system costs about £11,250, or £3,750 after the £7,500 grant, paying back in about 19.9 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
£188 /yr saved
Heat pump £895/yr · payback 19.9 yrs
On a heat pump tariff (~15p/kWh)
cheap-rate electricity
£569 /yr saved
Heat pump £514/yr · payback 6.6 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
- £1,083/yr
- Gas standing charge saved
- £106/yr
- Indicative system size
- ~6kW
- Install after grant
- £3,750
- CO₂ saved
- 1,730 kg/yr
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Estimate only. Real figures depend on your home, install and tariff. Prices: Ofgem cap, Jul-Sep 2026.