Should you switch?
The honest answer turns on three things. First, cost: the grant takes £7,500 off the upfront price, and on the current price cap a heat pump’s running cost is close to gas. Second, timing: replacing a working boiler on your own schedule is far easier than replacing a broken one in January, when the quickest fix is another boiler. Third, the house: a heat pump needs space for an outdoor unit and a cylinder, and may need bigger radiators. None of those rules most homes out, but each one is a question for the survey.
The grant only works if the heat pump replaces the boiler. GOV.UK says there is no grant for a hybrid system that keeps a boiler running alongside; the hybrid vs air source comparison sets out when that trade-off is worth it.
The grant for gas homes
Under the Boiler Upgrade Scheme, an owner in England or Wales replacing a gas boiler gets £7,500 off an air source or ground source heat pump. The higher £9,000 band is not for gas homes: it needs no mains gas connection and an oil or LPG system being replaced. Gas homes are the scheme’s largest group, 55% of the grants paid by end of September 2026.
On price, the DESNZ median installed cost of a grant-funded air source heat pump was £12,826 in 2026 Q3, including the grant value, so the middle of the market leaves about £5,326 to pay. Installing a heat pump in a home is 0% VAT until 31 March 2027, then 5%. Get a boiler replacement price at the same time, so you are comparing the real alternative.
What comes out, what goes in
| Item | Gas boiler home | After the heat pump |
|---|---|---|
| Heat source | Boiler on a wall indoors | Outdoor unit, about the size of two wheelie bins side by side (Energy Saving Trust) |
| Hot water | Often a combi with no tank | A hot water cylinder; the Energy Saving Trust says it can usually fit in a cupboard of at least 80cm x 80cm |
| Radiators | Sized for water at about 75°C | Run at a lower flow, often 35 to 45°C, so some may be enlarged |
| Gas supply | Needed | Can be capped if nothing else uses gas |
| Planning | None | Usually permitted development in England under Class G, within limits (one unit, 2 on a detached house; noise calculation) |
The cylinder is the change people most often underestimate. A combi boiler heats water on demand; a heat pump heats a stored tank. If you had a cylinder removed when a combi went in, the survey has to find a space for a new one. The cylinders guide covers sizes and positions.
Running costs against gas
At the Ofgem cap for 1 October to 31 December 2026, gas is 7.97p per kWh and electricity 26.32p. A gas boiler at 90% efficiency makes heat for about 8.9p per kWh; a heat pump at a seasonal efficiency of 3, about 8.8p. So on a standard tariff, expect roughly level running costs, not a large saving. The gains come from a good design (a higher efficiency), a heat pump tariff, and dropping the gas standing charge if you cap the supply. The running costs comparison has the full sum and a calculator.
The steps, survey to switch-on
- Check the grant. Own the home, in England or Wales, replacing gas: £7,500. The eligibility checker gives an indicative answer.
- Get surveys. An MCS-certified installer measures heat loss room by room and plans the unit, cylinder and radiators. Get more than one.
- Choose a quote. It should show the grant as a deduction and the balance you pay.
- The installer applies. Ofgem emails you to confirm consent within 14 days; the voucher then lasts 3 months for air source.
- Installation. The Energy Saving Trust says around 3 days is typical; you will be without heating and hot water for part of it.
- Commissioning and handover. Ask to be shown the controls and given the design figures in writing.
Living with it
A heat pump is run differently from a boiler. It works best low and steady, with the heating left on rather than blasted on and off, and with weather compensation turning the flow temperature down on mild days. Radiators feel warm rather than hot. If you treat it like a boiler, it costs more to run; the why is my heat pump electricity bill high guide covers the usual causes.