Facts last checked 17 September 2026
The short answer
At the Ofgem price cap for October to December 2026, electricity costs 3.3 times as much per kWh as gas, so a heat pump needs to deliver about 2.8 units of heat per unit of electricity just to match an 85% efficient gas boiler on unit costs. That is exactly the median measured in the government's Electrification of Heat trial. For a typical home using 9,500 kWh of gas a year, a heat pump at that median costs about the same to run as gas, and saves around £106 a year if you also close your gas account. At an efficiency of 3.2 that saving is about £200, and a tariff with cheaper hours can add more. A poorly designed system running at 2.5 costs more than gas on unit rates.
What decides whether a heat pump costs less to run than gas?
Three numbers, and nothing else, decide the comparison. Once you have them you can check any claim you are given, including ours.
- The price ratio: what you pay per kWh of electricity divided by what you pay per kWh of gas.
- Your boiler's real efficiency: the share of the gas it burns that ends up as heat in your home.
- The heat pump's seasonal performance factor (SPF): the heat it delivers over a year divided by the electricity it uses, measured in your home rather than claimed on a brochure.
The cost of a unit of heat from each is simple arithmetic. From gas: gas price ÷ boiler efficiency. From a heat pump: electricity price ÷ SPF. The heat pump is cheaper on unit costs when its SPF is higher than the price ratio multiplied by the boiler efficiency. Everything below is that sum, with the assumptions shown.
What do gas and electricity cost right now?
| Fuel | Unit rate | Standing charge | Standing charge per year |
|---|---|---|---|
| Electricity | 26.32p per kWh | 54.83p per day | £200.13 |
| Gas | 7.97p per kWh | 29.68p per day | £108.33 |
The price ratio is 26.32 ÷ 7.97 = 3.30. For July to September 2026 it was higher (26.11p against 7.33p, a ratio of 3.56), partly because electricity still carried VAT then. Rates vary by region and payment method, and fixed tariffs differ, so use the figures on your own bill if you can.
What does a typical home actually pay? The worked numbers
Assumptions, so you can redo this: Ofgem's typical medium household gas use from July 2026 is 9,500 kWh a year, and we treat all of it as heating and hot water. The gas boiler turns 85% of that into heat, so the home needs 9,500 × 0.85 = 8,075 kWh of heat a year. The heat pump supplies the same 8,075 kWh. Prices are the October to December 2026 cap. The electricity standing charge is left out because you pay it either way.
| System | Energy bought | Unit cost per year | Difference vs gas (units only) | Difference vs gas (gas account closed) |
|---|---|---|---|---|
| Gas boiler, 85% | 9,500 kWh gas | £757 | n/a | n/a |
| Heat pump, SPF 2.5 (poorly designed) | 3,230 kWh electricity | £850 | £93 more | £15 less |
| Heat pump, SPF 2.8 (trial median) | 2,884 kWh electricity | £759 | £2 more | £106 less |
| Heat pump, SPF 3.2 (well designed) | 2,523 kWh electricity | £664 | £93 less | £201 less |
| Heat pump, SPF 3.6 (excellent) | 2,243 kWh electricity | £590 | £167 less | £275 less |
So on a standard tariff the honest range runs from paying about £93 more a year for a poor installation to saving about £275 for an excellent one. The single biggest lever inside that range is the quality of the design: correct sizing, a low flow temperature and radiators that match it.
What efficiency will your heat pump really achieve?
The Electrification of Heat demonstration project, funded by the government, metered air source heat pumps in real British homes. Across 291 systems with a full year of data, the median SPF was 2.80, and the middle half of homes fell between 2.53 and 3.09. The earlier Renewable Heat Premium Payment trial had a median of 2.44, so installations have improved, but the spread between good and poor ones has not narrowed much.
- Lower flow temperature, higher SPF: the trial found systems running cooler water performed better. Flow temperature is the temperature of the water leaving the heat pump for your radiators.
- Design floor: the Boiler Upgrade Scheme only funds systems designed to a seasonal coefficient of performance (SCOP) of at least 2.8, calculated with the MCS tool. A design figure is not a guarantee, but it rules out the weakest designs.
- Heat loss: an uninsulated home needs hotter water to stay warm, which pulls efficiency down. Insulation often improves the SPF as well as cutting the heat you need.
Ask any installer for the SCOP they have designed to and the flow temperature it assumes, in writing, alongside the room-by-room heat loss calculation that MCS rules require. If they cannot give you those three things, the running cost estimate is a guess.
How much difference does the tariff make?
A lot. The table above uses the standard capped rate for every kWh. Time-of-use tariffs, which charge less at certain hours, are worth asking suppliers about, because a heat pump with a hot water cylinder can shift some of its use into cheaper hours. What counts is the average price you pay across all the heat pump's electricity, which depends on the tariff and on how much of the load can move.
| Average price you pay | SPF 2.8 | SPF 3.2 |
|---|---|---|
| 26.32p (price cap) | £759 | £664 |
| 20p | £577 | £505 |
| 15p | £433 | £379 |
These average prices are illustrations, not quotes from any supplier. Look up the current rates for any tariff you are considering, check its standing charge too, and redo the sum with your own numbers. If you also have solar panels, some of the heat pump's daytime electricity can come from your roof; see our solar guides.
What about smaller and larger homes?
Ofgem's typical consumption figures from July 2026 are 6,000 kWh of gas a year for low users, 9,500 for medium and 14,000 for high. The same method, at the same 85% boiler efficiency and price cap rates, gives this.
| Gas use per year | Gas boiler | Heat pump, SPF 2.8 | Heat pump, SPF 3.2 |
|---|---|---|---|
| 6,000 kWh (low) | £478 | £479 | £419 |
| 9,500 kWh (medium) | £757 | £759 | £664 |
| 14,000 kWh (high) | £1,116 | £1,119 | £979 |
Notice that the standing charge saving is the same £108 whatever the size of the home, so it matters proportionally more in a small flat, while the efficiency gain matters more in a large house.
What could change these numbers?
- Boiler efficiency: if your boiler really achieves 90%, gas heat costs 8.9p per kWh and the break-even SPF rises to about 2.97. If your old boiler achieves less than 85%, the heat pump looks better than our table.
- Price cap changes: Ofgem resets the cap every three months. Gas and electricity do not move together: this October the gas unit rate rose by about 9% while electricity rose by under 1%.
- Servicing: both systems should be serviced. Compare the actual quotes rather than assuming either is free.
- Off the gas grid: against heating oil, LPG or electric storage heaters the comparison is very different. See on-gas vs off-gas heating.
How do you work out your own numbers?
- Find your annual gas use in kWh on a recent bill or your supplier's app.
- Multiply by your boiler's efficiency (use 0.85 if you do not know) to get the heat you need.
- Divide that by a realistic SPF. Use the design SCOP from a proper quote, or 2.8 as a cautious middle.
- Multiply the result by the electricity price you would actually pay. That is the heat pump's running cost.
- Compare with your current gas unit cost, and add back the gas standing charge if you would close the account.
Running costs are only half of the decision; the other half is what the system costs to install after the grant. Our payback tool combines the two, and the Boiler Upgrade Scheme checker confirms whether £7,500 comes off your quote.
Common questions
Is a heat pump cheaper to run than a gas boiler?
At the October to December 2026 price cap, a heat pump with the trial median efficiency of 2.8 costs about the same as an 85% gas boiler on unit rates, and about £106 a year less for a typical home if you close your gas account. Better design or a heat pump tariff increases the saving. A poor installation can cost more.
How much electricity does a heat pump use a year?
Heat needed divided by SPF. A typical medium gas home needs about 8,075 kWh of heat, so at an SPF of 2.8 the heat pump uses about 2,884 kWh, and at 3.2 about 2,523 kWh. This is on top of your normal household electricity.
Should I keep my gas connection after getting a heat pump?
Only if you still cook with gas. Otherwise the gas standing charge, £108.33 a year at the October to December 2026 cap, is money spent on a connection you do not use. Ask your supplier how to close the account safely.
Why do some people say their heat pump bills went up?
Usually because the system runs below the price ratio: undersized or oversized, radiators too small so the flow temperature is high, controls set up like a gas boiler, or a home with high heat loss. On a standard tariff, an SPF of 2.5 costs about £93 a year more than gas for a typical home.
What SCOP should I ask an installer for?
The Boiler Upgrade Scheme requires a designed SCOP of at least 2.8. Ask for the design SCOP, the flow temperature it assumes and the heat loss calculation behind it, all in writing.
Does the VAT cut on electricity make heat pumps worth it?
It helps. It lowers the break-even efficiency from about 2.95 to about 2.8 against an 85% gas boiler. It runs from 1 October 2026 to 31 March 2027, so do not base a long-term decision on it alone.