How much does a heat pump cost to install in the UK? Here's where the money goes

For most three-bed semis in Kent, a full air source heat pump install runs somewhere between £9,000 and £15,000 before any grant. The £7,500 Boiler Upgrade Scheme grant comes straight off that, so most people end up paying somewhere between £1,500 and £7,500 out of their own pocket. That range is wide because the number that actually matters isn’t the unit on the wall. It’s what happens around it.

I quoted a heat pump job in Ashford last spring where the homeowner had three quotes: £8,200, £11,600 and £14,900. Same house, same postcode, same brand of pump on two of the three. The cheap one skipped the heat loss survey and specced the smallest unit that would technically do the job, on the radiators already in the house. It would have worked, in the sense that the house would have been warm. It would also have run at a high flow temperature every day for the next fifteen years, because nobody sized the emitters properly, and a heat pump on a high flow temperature is barely cheaper to run than the boiler it replaced.

That’s the bit people miss. The cheapest quote is usually the most expensive one, just not on the invoice. It’s expensive on the electricity bill, every winter, for as long as you own the pump.

So where does the money in a proper quote actually go? Roughly a third is the pump itself and the hot water cylinder. Roughly a third is labour, and it’s more labour than a boiler swap, because you’re usually running new pipework, fitting a bigger cylinder, and doing electrical work for a unit that draws more current than a gas boiler ever did. The last third, and the bit that gets cut first when someone’s trying to hit a low number, is the design work: the heat loss survey, the radiator sizing, and often swapping a handful of undersized radiators so the whole system can run cooler. Skip that third and you save perhaps £2,000 up front. You lose more than that back in higher bills before the pump’s even five years old.

The grant makes the sums easier than most people expect, and I think that surprises people because they’ve heard the horror stories about renewables being unaffordable. £7,500 is not a discount voucher, it’s not means-tested, and it’s not tied to your income. If your install qualifies, which almost all straightforward retrofits do, it comes off the price like a builder’s discount. On a £10,500 job that’s a final bill of £3,000, which is not far off what a lot of people pay for a new gas boiler and a few new radiators anyway.

What I can’t do is quote you a single number, because the range genuinely depends on your house. A well-insulated new build in Sittingbourne with modern radiators might need very little beyond the pump and cylinder. An old cottage with single-glazed sash windows and radiators sized for a boiler running at 70°C will need proper design work to get the flow temperature down where a heat pump is happy, and that costs more upfront and saves you more for years afterwards. Neither of those houses is wrong to get a heat pump. They just need a different quote, and a different conversation before anyone signs anything.

If someone gives you a number in the first five minutes, before they’ve asked about your radiators, your insulation, or how many bedrooms are cold in January, that number isn’t a quote. It’s a guess dressed up as one.