Chat with an expert
A gas boiler is cheaper to buy. Whether a heat pump is cheaper to run depends on three things: how efficient the boiler it replaces is, the electricity tariff the heat pump runs on, and how well the system is sized for the house.
What each system costs to install
- Gas boiler: a like-for-like combi replacement is typically £2,500 to £4,000 fitted, more if the boiler type or its position changes (Checkatrade cost guide, 2026).
- Air source heat pump: the median cost of an installation under the Boiler Upgrade Scheme was £13,021 in the 2025/26 scheme year, including the unit, the installer’s fees and the home upgrades done alongside it (government scheme statistics). The £7,500 grant comes off that, so about £5,500 for a typical home in England or Wales.
How efficient each system is
- Gas boiler: a new boiler runs at about 85% in practice, and an old boiler due for replacement at around 75%, on the Energy Saving Trust’s figures. For every unit of gas you buy, you get less than one unit of heat.
- Air source heat pump: the Electrification of Heat trial, which fitted 742 heat pumps in homes rated EPC A to G, measured a median of 2.8 units of heat for every unit of electricity. A well-set-up system gets three; a poorly sized one gets less.
Which is cheaper to run?
On a standard flat-rate electricity tariff, most heat pumps cost about the same to run as an efficient new gas boiler, and some cost more, because a unit of electricity costs several times a unit of gas (Energy Saving Trust). Three things change that:
- A heat pump tariff: cheaper off-peak electricity for heating. Heat pumps on a dedicated tariff ran at a lower cost than a gas boiler in the Energy Saving Trust’s analysis.
- The boiler you are replacing: against a 75% boiler, a heat pump is cheaper to run on most tariffs.
- Leaving gas altogether: no gas standing charge, which at July 2026 prices was about £105 a year (Energy Saving Trust).
Nesta, the innovation charity whose heat pump analysis is widely used in the sector, models annual running costs at about £700 for a gas boiler and £580 for an air source heat pump, and, with the grant, total annualised lifetime costs within £20 of each other. Your own figures depend on your tariff, so ask any installer for a running-cost calculation for your house, with the assumptions written down.
Cost comparison at a glance
| Factor | Gas boiler | Air source heat pump |
| Installation | £2,500 to £4,000 for a like-for-like replacement | £13,021 median before the grant, about £5,500 after |
| Efficiency in practice | About 85% new, 75% old | Median 2.8 units of heat per unit of electricity |
| Running cost | About £700 a year, modelled | About £580 a year on a suitable tariff, modelled; similar to gas on a flat tariff |
| Grant | None | £7,500 in England and Wales |
| Policy | Government plans to phase out new gas boiler installations from 2035, with exemptions for homes that are not suitable | Eligible under the Boiler Upgrade Scheme to 2030 |
Is a heat pump right for you?
A heat pump suits a house that can hold heat at the lower flow temperature it runs at, with radiators big enough to give that heat out, room for a hot water cylinder and a place for the outdoor unit. The Electrification of Heat trial installed them in every property type it tested, including older and poorly rated homes, so age alone does not rule a house out. What decides it is measurement.
A gas boiler remains the practical choice where the upfront cost has to be lowest, where you are moving soon, or where the survey shows the house would need insulation and new radiators first and you are not ready to do that work.
Before you decide
A quote does not tell you whether your house can hold heat at the lower temperature a heat pump runs at. A heat pump survey measures that: heat loss by room, insulation, radiator sizes, cylinder space and where the outdoor unit can sit. The visit is non-invasive and the assessor does not quote for the work, so the report is independent of whoever installs. Inter Infinity carries out heat pump surveys as part of a retrofit assessment across London and Kent. How the grant is claimed and how heat pumps work are covered separately.
Sources
- Heat pump fact check and air source heat pumps, Energy Saving Trust, read 9 October 2026
- Boiler Upgrade Scheme statistics: July 2026, Table A1.3A, Department for Energy Security and Net Zero, from Ofgem and MCS installation data
- Seven reasons we still need heat pump subsidies, Nesta, running-cost model
- Electrification of Heat demonstration project, performance findings and project summary, Energy Systems Catapult
- Heat and Buildings Strategy, gov.uk
- New boiler costs in 2026, Checkatrade cost guide
