Key takeaways
- Heat pump install cost after the £7,500 BUS grant typically lands at £6,000–£10,000 for a well-insulated home; gas boiler swap is £2,500–£4,500.
- On a standard variable tariff, a heat pump in a well-insulated semi runs at roughly the same annual cost as a modern condensing gas boiler — sometimes a bit less, sometimes a bit more.
- On a heat pump-friendly tariff (Cosy, Octopus Heat Pump, Intelligent Go), running costs typically drop 20–30% below gas.
- In a poorly insulated 1930s solid-wall house with no plans to upgrade fabric, a gas boiler will usually still be cheaper to run.
- Tenure matters: if you'll move in under five years, the payback case for a heat pump weakens unless it adds resale value.
- Over 25 years on a green tariff, heat pumps win on lifetime cost in most modern homes, but only modestly — this is a long game, not a quick win.
The heat pump versus gas boiler question gets argued in extremes. One side says heat pumps are a no-brainer that will halve your bills. The other says they're an expensive con that doesn't work in British weather. Neither is true. The honest answer is "it depends on your house, your tariff, and how long you plan to live there" — and the goal of this article is to give you the numbers to work that out for yourself.
This article walks through the numbers in five passes: install costs after the BUS grant, running cost per kWh of delivered heat, 25-year scenarios across three reference homes, the cases where gas still wins, and the practical caveats most articles skip. Read the section that matches your situation; skip the rest.
Install costs in 2026
Let's start with what you actually pay on day one. Prices vary by region and installer, but the typical 2026 ranges look like this:
| System | Typical install (before grant) | Grant available | Net cost to homeowner |
|---|---|---|---|
| Combi gas boiler (like-for-like swap) | £2,500–£4,500 | None | £2,500–£4,500 |
| System gas boiler with cylinder | £3,500–£6,000 | None | £3,500–£6,000 |
| Air source heat pump (8kW, ready home) | £12,000–£15,000 | £7,500 (BUS) | £4,500–£7,500 |
| Air source heat pump (with rad upgrades + cylinder) | £14,000–£18,000 | £7,500 (BUS) | £6,500–£10,500 |
| Ground source heat pump (small bore) | £20,000–£30,000 | £7,500 (BUS) | £12,500–£22,500 |
The BUS (Boiler Upgrade Scheme) grant is £7,500 for air or ground source heat pumps in England and Wales, with equivalent schemes in Scotland and Northern Ireland. The grant is paid to the installer and shows up as a discount on your quote. It's available until at least 2028.
So the honest position on capital cost is that a heat pump install is roughly two to three times the cost of a like-for-like boiler swap, even after the grant. That gap closes if your boiler has reached end-of-life and you'd be paying for a replacement anyway, because the comparison is then between £4,000 of gas vs £6,500 of heat pump — a much smaller real-world delta.
Be aware that quotes vary widely. A 2025 Which? survey found a 40% spread between the cheapest and most expensive MCS-certified quotes for the same house. Always get three quotes and check what's included — particularly whether radiator upgrades, a new cylinder, and electrical work (consumer unit upgrade if needed) are bundled in or extras. The cheap quote is rarely cheap by the time the variations land.
One often-overlooked install detail: the BUS grant requires no fossil-fuel boilers in the home post-install. You can't keep your gas boiler "as backup" and claim the grant. Some homeowners find this surprising — but it's not negotiable.
Running costs: the part most people get wrong
Running cost depends on three things: how much heat your house needs, what your gas and electricity unit rates are, and how efficiently each system converts fuel into heat.
A modern condensing gas boiler runs at about 88–92% efficiency. A well-installed air source heat pump runs at a seasonal coefficient of performance (SCOP) of 3.0–3.8 in a typical UK home, which means for every 1 kWh of electricity it delivers 3 to 3.8 kWh of heat. That's the maths that decides everything.
To put it in plain numbers, here's the cost per kWh of delivered heat across three tariff scenarios, using April 2026 cap pricing as a reference (approximately 6.3p gas, 27p standard electricity, 13p heat pump tariff):
| System | Standard tariff | Heat pump tariff (off-peak avg) | Green premium tariff |
|---|---|---|---|
| Gas boiler (90% eff) | ~7.0p / kWh heat | n/a | ~7.0p / kWh heat |
| Heat pump (SCOP 3.0) | ~9.0p / kWh heat | ~4.3p / kWh heat | ~10p / kWh heat |
| Heat pump (SCOP 3.5) | ~7.7p / kWh heat | ~3.7p / kWh heat | ~8.5p / kWh heat |
| Heat pump (SCOP 3.8) | ~7.1p / kWh heat | ~3.4p / kWh heat | ~7.8p / kWh heat |
What this table tells you bluntly: on a standard tariff, a typical heat pump is roughly cost-neutral with gas. On a heat pump-specific tariff like Cosy or Octopus Heat Pump, it's meaningfully cheaper. On the most expensive green premium tariffs, the heat pump can actually cost slightly more to run than gas — which is the scenario that fuels most of the negative coverage you've read.
This is also why SCOP matters so much. The difference between a poorly commissioned heat pump (SCOP 2.5) and a well-commissioned one (SCOP 3.8) is roughly 50% in running cost. The single biggest predictor of SCOP is the design flow temperature: low-temperature systems (35–45°C) deliver high SCOP, high-temperature systems (55–65°C) deliver low SCOP. A good installer designs the radiators to match a low flow temperature; a bad one whacks the flow temperature up to compensate for undersized emitters and the SCOP collapses.
The practical implication: don't accept a quote without seeing the heat loss calculation per room and the flow temperature target. If the quote is silent on these, it's a red flag.
25-year scenarios by house type
The annual heat demand is what drives the running cost gap into pounds and pence. We'll use three reference homes:
- Terraced: 80 m², EPC C, ~9,000 kWh/year heat demand
- 3-bed semi: 100 m², EPC C, ~12,000 kWh/year heat demand
- 4-bed detached: 150 m², EPC C, ~17,000 kWh/year heat demand
Across 25 years, with an annual energy price inflation assumption of 3% (gas and electricity rising in parallel), here's how it lands on a heat-pump-friendly tariff with SCOP 3.5:
The lifetime saving on a heat pump tariff lands at roughly £5,700 (terraced), £7,500 (semi), and £10,500 (detached). Subtract the higher install cost and net lifetime saving is typically £1,500–£6,000 across the three house types. That's not life-changing money over 25 years — it's modest. But it's the right direction, and crucially it doesn't tie you to the gas grid.
Two factors can shift this materially. First, replacement cycles: the BUS grant is currently committed to 2028 and it's plausible (not certain) that the next government tightens or extends. Second, gas standing charges: gas standing charges are politically sensitive and have been creeping up. If gas standing charges hit £200/year as some forecasts suggest, the heat pump case improves further because the comparison gets closer when you remove gas entirely vs keeping a £200/year gas connection just for cooking.
The detached house case is the most decisive. Higher heat demand means higher absolute savings, and the install cost premium amortises across more usage. If you're in a 4-bed detached and planning to stay 10+ years, the heat pump case is hard to argue against on long-run economics.
When gas still wins
There are real cases where a heat pump is the wrong call right now. We don't sugar-coat them:
- Solid-wall, no insulation plans, large radiators not viable: SCOP drops below 2.5 and running costs exceed gas. Fix the fabric first, then revisit.
- Selling within five years: EPC uplift won't fully recover the install premium unless your local market is heat pump aware.
- Tight outdoor space and listed building constraints: Without a workable position for the outdoor unit, this becomes structurally hard.
- You only run heating two months a year: Low utilisation extends payback beyond useful life.
If any of those apply, a high-efficiency condensing boiler with smart controls and a transparent plan to revisit in 5–10 years is the honest answer.
The carbon angle
Even on a standard grid mix, a heat pump emits roughly 60% less CO₂ per kWh of heat than a gas boiler in 2026, because the UK grid is now around 40% renewable on average and improving every year. On a 100% renewable tariff, the heat pump's operational footprint approaches zero. Gas is gas — it won't get cleaner unless hydrogen blending becomes meaningful, which the National Infrastructure Commission has now ruled out for most of the residential network.
If you take operational carbon as the deciding factor (rather than money), the heat pump wins clearly even before you adjust for embodied carbon of manufacturing. The embodied carbon of a typical air source heat pump is roughly 800–1,200 kg CO₂; a gas boiler is roughly 200–300 kg CO₂. The heat pump pays back its embodied carbon premium in 12–18 months of operation. Over a 20-year life, the carbon delta widens enormously.
Hot water nuances
One real friction point worth flagging: heat pumps heat hot water to 50–55°C, with a weekly Legionella cycle to 60°C+. Gas boilers heat water to 60°C+ continuously. If you have small children, dishwashing without a dishwasher, or anyone who likes a really hot bath, the practical difference is noticeable.
You compensate two ways: a slightly larger cylinder (200–250L instead of 150–180L) and a thermostatic mixing valve that limits delivery to 43–48°C anyway for safety. Most heat pump-installed homes report no practical hot water complaints after the first month, but it's worth being aware that the thermal experience changes.
FAQ
Will my radiators need replacing?
Some will, some won't. A good MCS-certified installer does a room-by-room heat loss survey and tells you which radiators need to grow. In a typical EPC C semi, you'd usually swap 2–4 radiators out of 8–10. Budget £150–£300 per radiator including labour.
Do heat pumps work in winter?
Yes. The published SCOP figures already account for cold months. UK winters are mild compared to Scandinavia and Canada, where heat pumps are mainstream. They are fundamentally not a hot-summer technology.
Are they noisy?
A modern unit at 1m runs at 40–50 dB — quieter than a fridge in your kitchen. Permitted Development rules require under 42 dB at the nearest neighbour boundary, so siting it sensibly handles this in nearly all cases.
What about hot water?
An air source heat pump heats your hot water cylinder to 50–55°C directly, then runs a brief weekly Legionella cycle to 60°C. You lose the instant on-demand combi feel, but you gain stored capacity. This is the biggest behavioural change.
Can I keep my gas boiler as backup?
Hybrid systems exist but are rare in 2026 — most installers no longer recommend them because the duplicated capital cost rarely justifies the small efficiency gain. Better to size the heat pump correctly first time.
What happens if energy prices change?
The headline risk for heat pumps is the gas:electricity price ratio. If gas prices drop dramatically and electricity stays high, gas wins. Most independent forecasts show the opposite trajectory through 2030, but it's worth flagging as a real uncertainty.
What this means for your decision
If you're in a reasonably insulated home (EPC C or better), planning to stay 7+ years, and willing to switch to a heat pump tariff, the heat pump case is now solid — modest lifetime savings plus genuine carbon reduction plus future-proofing against gas grid decarbonisation. If your home needs serious fabric work first, do that work first and revisit. If you're moving soon, a high-efficiency boiler with smart controls is the honest answer.
Run your own numbers with the heat pump vs gas boiler calculator on EcoSavingHub — it uses your actual postcode, house type, and tariff to give a personalised 25-year comparison.
Want to model your specific home? Use our free ROI calculators →