Heat pump vs gas boiler: what it really costs
For a typical 3-bedroom semi (about 12,000 kWh/yr), an air source heat pump (SCOP 3.5) costs about £902/yr to run versus about £1,171/yr for mains gas. That is about £269 saved a year. Use the calculator to put in your own home and tariff.
Running cost compared, by home size
Typical yearly running cost of an air source heat pump (SCOP 3.5) against mains gas, at the national Ofgem price cap, for five common UK homes. Every figure comes from the same model as the calculator below.
| Home | Heat kWh/yr | Gas boiler £/yr | Heat pump £/yr (cap) | Heat pump £/yr (HP tariff) | Saving/yr |
|---|---|---|---|---|---|
| 1 bed flat | 4,500 | £507 | £338 | £193 | £168 |
| 2 bed terraced house | 8,000 | £817 | £602 | £343 | £215 |
| 3 bed semi-detached house | 12,000 | £1,171 | £902 | £514 | £269 |
| 4 bed detached house | 19,250 | £1,813 | £1,448 | £825 | £365 |
| 5+ bed detached house | 24,000 | £2,234 | £1,805 | £1,029 | £429 |
At the national price cap a heat pump undercuts mains gas on running cost once its SCOP is above about 3.0, and a typical air source heat pump runs at SCOP 3.5; dropping the gas standing charge widens the gap further. Heat pump cost = yearly heat ÷ SCOP × the electricity unit price; mains gascost = heat ÷ 0.9 boiler efficiency × the fuel price, plus the gas standing charge you can save. Prices are the Ofgem cap (Oct-Dec 2026); full model in the methodology.
For the same comparison worked line by line on a 3-bed semi, including the SCOP figure the whole answer turns on, read do heat pumps actually save money.
Your standard rate. The tariff scenario is shown separately.
Efficiency. 3.5 is typical.
On a standard tariff (price cap)
electricity at 26.32p/kWh
£269 /yr saved
Heat pump £902/yr · payback 14 yrs
On a heat pump tariff (~15p/kWh)
cheap-rate electricity
£657 /yr saved
Heat pump £514/yr · payback 5.7 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
- £1,171/yr
- Gas standing charge saved
- £108/yr
- Heat pump electricity use
- 3,429 kWh/yr (~286/month)
- 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, Oct-Dec 2026.
The tariff you are on matters more than the house
Every figure above uses the 26.32p/kWh price cap. A dedicated heat pump tariff runs nearer 15p in its cheap windows, roughly 43 percent off the unit rate, which moves the running cost further than any change to the property itself.