Guide · Costs
Cost to replace a gas boiler with a heat pump
What changes, what stays, and what the swap actually costs after the grant.
Replacing a gas boiler with an air source heat pump costs £9,000–£14,000 installed in 2026, or roughly £1,500–£6,500 after the £7,500 Boiler Upgrade Scheme grant (GOV.UK, 2026). The extra work over a like-for-like boiler swap is the hot water cylinder, any radiator upsizing, and a dedicated electrical supply.
We’re funded by installer referral fees when you request quotes. Our editorial coverage isn’t paid for — read our editorial policy and how we rank installers.
What gets removed and what replaces it
- Combi boiler out; outdoor heat pump plus indoor hydraulic module in.
- A hot water cylinder becomes essential — combis have none.
- Gas supply to the boiler is capped; the gas meter can stay for a hob.
- Flue is removed and the wall made good.
- A new dedicated circuit runs from the consumer unit to the outdoor unit.
The three costs people forget
Cylinder space. If you have a combi, you need somewhere for a 150–250 litre cylinder. Losing a cupboard is a real cost even when it is not on the quote.
Radiator upsizing. Heat pumps run cooler water, so some radiators need to be larger. In most homes it is a handful of rooms, not the whole house.
Electrical work. A load assessment plus a new circuit is typical, and some properties need a supply upgrade from the network operator.
Running cost impact
Whether your bills fall depends on the seasonal efficiency you achieve and the tariff you are on. With a SCOP above 3.5 and a heat pump tariff, running costs are usually similar to or lower than a modern gas boiler; with poor insulation and a standard tariff they can be higher.
Frequently asked questions
- Can I keep my radiators when swapping to a heat pump?
- Usually most of them. A room-by-room heat loss calculation identifies which need upsizing to work at lower flow temperatures.
- Do I have to remove my gas boiler to get the £7,500 grant?
- The Boiler Upgrade Scheme requires the fossil fuel system to be replaced, so the boiler is decommissioned as part of the install. Hybrid systems are not eligible.
- How long does the swap take?
- Typically two to four working days for a straightforward retrofit, longer if radiators and pipework are being replaced.
- Boiler Upgrade Scheme — GOV.UK — Official guidance on the £7,500 BUS grant in England and Wales.
- Energy Saving Trust — Heat pump efficiency, running cost and SCOP benchmarks (UK).
- Ofgem — UK energy regulator — current electricity unit rates and standing charges.
Start now — it’s free
Get matched with MCS-certified installers
Up to three free, no-obligation quotes from vetted local installers. 60-second form.