Heat Pump vs Gas Boiler Running Cost Calculator

What a kWh of Heat Costs

A gas boiler turns about 90% of the gas it burns into heat. A heat pump moves heat from the outside air, and its seasonal performance (SCOP) is how many kWh of heat you get for each kWh of electricity over a year. At the cap (26.32p a kWh for electricity, 7.97p for gas, Direct Debit averages for England, Scotland and Wales), on a standard tariff:

So on a standard tariff a heat pump has to average a SCOP of about 3.0 to match gas. What real ones manage varies a lot. The government's Electrification of Heat trial measured a median of 2.80 across 291 heat pumps installed in 2020 and 2021, below that break-even. The 307 air and ground source systems on heatpumpmonitor.org with a full year of data average 4.01, though their owners chose to publish them. We plan on 3.5, between the two. We'd ask each installer for the SCOP their design is predicted to reach, in writing. On a heat pump tariff, at our estimate of a 20p blended rate, the break-even drops to a SCOP of about 2.3, and SCOP 3.5 gives 5.7p a kWh of heat.

Why Gas Used to Win

Under the April to June 2026 cap, the same sums gave 7.0p a kWh of heat from the heat pump against 6.4p from gas, so gas was cheaper. From July (1 July to 30 September 2026) the heat pump was ahead, 7.5p against 8.1p. In October gas went up 8.7% and electricity 0.8%. Electricity's rise was small only because VAT came off it: there's none from 1 October 2026 to 31 March 2027, and before VAT it went up about 6%. If 5% VAT came back on today's rate with nothing else changing, SCOP 3.5 would cost 7.9p a kWh of heat, still under gas, but prices will have moved by then. The calculator above lets you set your own price rises.

A Year's Heating in a Typical 3-Bed

DESNZ's measured gas use for 3-bedroom homes in England and Wales (median to mean) works out at about 9,500 to 10,300 kWh of heat a year through a 90% boiler. At the cap:

• Gas boiler: £840 to £910 a year
• Heat pump, standard tariff: £710 to £770 a year, £130 to £140 less
• Heat pump, heat pump tariff: £540 to £590 a year, £300 to £320 less

Two things move those savings. Servicing: British Gas charges £189 for a one-off heat pump service and £119 for a boiler, so the heat pump costs about £70 a year more to look after. And the gas standing charge, about £108 a year, which you only stop paying if you have the gas supply taken out (not if you keep a gas hob; we haven't counted any charge for taking it out). Put together:

Upfront Costs and Payback

The DESNZ Boiler Upgrade Scheme statistics put the middle half of air source installs at £11,100 to £15,600 in April to June 2026 (median £12,908), and the 2025/26 median for a 6 to 8kW install, which we use as the example here, at £12,200. The £7,500 grant brings that to £4,700, against about £2,750 for a new combi. Radiators that need upsizing come on top; see our heat pump costs guide.

How long the heat pump takes to pay for itself out of the yearly figures above, at today's prices:

Air source heat pumps typically last 15 to 20 years and gas boilers 10 to 15, according to Intergas and OVO. The calculator above runs 15 years, adds each year's servicing and starts both price rises at 0%. It shows the year it breaks even, so it reads one year later than the paybacks in this table. It doesn't add a second new boiler within those years, which flatters the boiler a little.

When the Boiler Still Comes Out Ahead

• You'd stay on a standard tariff. Unless you have the gas taken out and your boiler is due anyway, the payback is longer than the heat pump lasts.
• The install would run below the break-even SCOP. Ask each installer what SCOP their design gives and at what flow temperature.
• You can't get the grant. Without it, even the best case above takes over 20 years (beyond the heat pump's life).

There's no ban on replacing a gas boiler with a new one in an existing home; see the gas boiler ban explained.

Scotland and Northern Ireland

The Boiler Upgrade Scheme covers England and Wales. In Scotland, Home Energy Scotland offers a grant of up to £7,500 towards a heat pump (£9,000 for eligible rural and island homes), plus an optional interest-free loan of up to £7,500; our heat pump grants guide has the conditions. The prices on this page are Ofgem's cap, which covers England, Scotland and Wales. In Northern Ireland, put your own gas bill in and turn the grant off; the tariff options are GB prices, so treat the result as a rough guide.

Getting Started

Put your own gas bill into the calculator and try both tariffs. Then get quotes: ask each installer for the heat loss calculation, the heat pump size and the SCOP their design gives. Our heat pump running costs guide and best heat pump tariffs go further.