Heat pump running costs vs a gas boiler: the honest sums
Written by Danny Whitfield
Heating and energy writer · Last updated 13 July 2026
Checked against GOV.UK: 10 July 2026 · Last verified: 13 July 2026
On a standard electricity tariff, a well-installed heat pump costs about the same to run as a gas boiler. On a dedicated heat pump tariff, most homes save £100 to £300 a year. A badly designed system can cost more than gas, which is why installation quality decides everything.
Every comparison you read either comes from someone selling heat pumps or someone who hates them. The arithmetic is not actually hard, so here it is with the assumptions on show, and you can rerun it with your own numbers.
The core arithmetic
A gas boiler turns 1 kWh of gas (about 6p) into roughly 0.85 kWh of heat, so a kWh of heat from gas costs about 7p.
A heat pump turns 1 kWh of electricity (about 24p standard rate) into about 3 kWh of heat at a seasonal COP of 3, so a kWh of heat costs about 8p. Nearly level, with gas slightly ahead.
Two levers move the result. A heat pump tariff with off-peak rates around 15p drops the cost to about 5p per kWh of heat, cheaper than gas. And a better-installed system running at COP 3.5 or 4 drops it further. Both levers together beat gas comfortably.
A year of heating, three ways
| Setup | Cost per kWh of heat | Annual cost |
|---|---|---|
| Gas boiler, 85% efficient | ~7.1p | ~£850 plus ~£100 standing charge share and service |
| Heat pump, COP 3, standard tariff | ~8.0p | ~£960 |
| Heat pump, COP 3.3, heat pump tariff | ~5.5p | ~£660 |
The middle row is why sceptics say heat pumps cost more, and on a standard tariff with a mediocre install, they do, by around £110 a year on these numbers. The bottom row is why owners of well-designed systems report savings. Same physics, different tariff and installation quality.
What decides your COP
- Flow temperature. Radiators run at 40 to 45 degrees beat 55 degrees. Bigger radiators allow lower temperatures.
- System design. A room-by-room heat loss calculation is required under MCS rules. Refuse any quote without one.
- Weather compensation switched on. It is free efficiency and some installers still leave it off.
- Running it steadily. Heat pumps like long low-and-slow running, not the on-off cycling habits of a boiler.
Do not forget the capital side
Running costs are only half the sum. The £7,500 Boiler Upgrade Scheme grant (£9,000 for oil and LPG homes) closes most of the up-front gap between a heat pump and a boiler, and a heat pump typically lasts 15 to 20 years against 10 to 15 for a boiler. The full purchase maths is in our heat pump cost guide.