Heat pump vs gas boiler: an honest comparison
Heat pumps are not strictly better than gas boilers, and gas boilers are not strictly cheaper. It depends on your property, your tariff and your time horizon. This guide compares them on the criteria that actually matter.
Quick answer
Over 15 years, a heat pump typically costs a UK 3-bed semi £25,700 in total versus £31,700 for a gas boiler, once install, servicing, running costs and carbon are counted1. Heat pumps cost more upfront even after the £7,500 grant, but win on lifespan and emissions, cutting CO₂ by roughly 80%. Gas still wins on install simplicity and instant hot water from a combi.
Key facts
- Install cost gap
- Gas £2,500 to £4,500 vs heat pump £2,500 to £6,500 net
- Carbon cut with heat pump
- ~80% less CO2 vs gas
- Lifespan
- Gas 10 to 15 years vs heat pump 15 to 20 years
- 15-year total cost, 3-bed semi
- Gas £31,700 vs heat pump £25,700
At-a-glance
| Criterion | Gas boiler | Heat pump (ASHP) |
|---|---|---|
| Install cost | £2,500 – £4,500 | £10,000 – £14,000 (gross), £2,500 – £6,500 after BUS |
| Annual running cost (3-bed semi, 2026 cap) | £1,100 – £1,500 | £900 – £1,400 |
| Lifespan | 10–15 years | 15–20 years |
| Servicing | £90 / year + boiler cover | £150 – £250 / year |
| Outdoor space needed | None | 1.5 m clearance from outdoor unit |
| Radiator upgrades typical? | Rare | Often 1–3 needed |
| Carbon (kg CO₂e / year, 3-bed) | ~2,200 kg | ~450 kg (and falling as grid decarbonises) |
Where heat pumps win
- Lower carbon, today. A UK ASHP at SCOP 3.5 emits roughly 80% less CO₂ than a gas boiler. The gap widens every year as the grid decarbonises.
- Running costs, with the right tariff. On a heat-pump-friendly time-of-use tariff (Octopus Cosy, EDF, etc.) the running cost gap can swing 20–30% in the heat pump's favour. On the standard variable rate, gas is usually slightly cheaper to run.
- Lifespan. Heat pumps typically last 15–20 years, gas boilers 10–15. Over a 20-year horizon you may replace a gas boiler twice.
- Future-proofing. Gas boiler bans in new-build came in for 2025. Government direction of travel is toward low-carbon heat; expect gas-related running costs and standing charges to keep rising.
- Cooling. Most modern ASHPs can run in reverse for summer cooling. A gas boiler cannot.
Where gas boilers still win
- Up-front cost. Even after BUS, a heat pump install costs more than a like-for-like boiler swap.
- Simplicity of retrofit. Replacing one gas boiler with another is a 1-day job. A heat pump install is 2–5 days plus design.
- Old, leaky properties. A heat pump can heat a Victorian terrace with single-glazed windows, but it needs careful sizing and you'll spend more on radiators. A gas boiler can over-pump heat into a leaky house at the cost of bills.
- Hot taps right now. A combi gas boiler delivers instant hot water from the tap. A heat pump needs a stored cylinder.
The retrofit question
For a well-insulated property, a heat pump is almost always the better long-term choice. For a draughty, leaky property, the right order is: insulation first, then heat pump. The Boiler Upgrade Scheme actually requires recent EPC recommendations on loft and cavity wall insulation to be implemented before you can claim.
15-year total cost of ownership
For a typical 3-bed semi in 2026, with current grant rates and a moderate gas/electric tariff:
| Gas boiler | ASHP | |
|---|---|---|
| Install (incl. one replacement at year 12 for gas) | £7,000 | £4,500 (after BUS) |
| Servicing × 15 years | £1,400 | £3,000 |
| Running costs × 15 years (rising 2% real) | £20,000 | £17,500 |
| Carbon cost (if priced at £100/tonne) | £3,300 | £700 |
| 15-year total | £31,700 | £25,700 |
Indicative only, your figures depend on property efficiency, tariff and grant changes. Source: 2026 install costs, current Ofgem cap (3-bed semi consumption averages from Ofgem), BUS rules.
When to choose what
Choose a heat pump if:
- Your property is reasonably well insulated, or you're willing to upgrade insulation first.
- You have outdoor space for the unit.
- Your 15-year horizon matters and you can use the BUS grant.
- You're willing to learn to use the system (lower flow temps, run it more steadily).
Choose a gas boiler if:
- You need a quick like-for-like replacement and can't accommodate a 2–5 day install.
- Your property is a heritage building with strict planning constraints on outdoor units.
- You are likely to move within 5 years and won't recover the up-front cost.
The comfort difference, not just the cost difference
Cost comparisons miss how the two systems actually feel to live with. A gas boiler blasts a room from cold to warm in minutes, a heat pump warms a house gradually over an hour or more, running more continuously at a lower output rather than cycling hard. Most heat pump owners describe the house as more evenly warm once they stop trying to run it like a boiler, no more cold mornings followed by a hot blast, just a steadier baseline temperature. Some people genuinely prefer the boiler's fast response and never adapt to the heat pump's rhythm; it's worth knowing this going in rather than discovering it after the install.
Noise and visual impact
A gas boiler is silent to a neighbour and mostly silent indoors beyond the flue fan. A heat pump's outdoor unit runs at 40 to 45 dB at 1 metre, audible but generally described as quieter than a fridge, and it's visible on an exterior wall in a way a gas boiler flue isn't. For most suburban properties this is a non-issue; for tightly packed terraces or conservation areas it's worth checking with neighbours and, where relevant, your local planning department before committing.
What the comparison doesn't capture
Total cost of ownership figures assume a stable gas/electricity price ratio over 15 years, which is unlikely. Gas prices are more volatile to geopolitical shocks; electricity prices are increasingly tied to renewable generation costs, which trend down over time. Standing charges are the other variable worth watching: removing a gas meter entirely saves the gas standing charge (currently around £110 to £130 a year), a saving the simple running-cost comparison above doesn't include because most homes keep gas for cooking during the transition.
A hybrid as a middle path
If the binary choice feels too stark, a hybrid system (heat pump plus retained gas boiler) sits between the two, lower upfront cost than a full heat pump, some of the carbon benefit, but it isn't eligible for the £7,500 BUS grant and typically works out more expensive over 15 years than either a full heat pump or a like-for-like gas boiler replacement once that grant is factored in. See our hybrid heat pumps guide for the full breakdown of when a hybrid genuinely makes sense.
If you're not replacing a boiler right now
This comparison assumes you're choosing between two live options today, but many homeowners are really asking "should I wait until my current boiler dies". If your boiler is under 10 years old and servicing cleanly, there's a reasonable case for waiting: heat pump technology, installer availability and grant rules are all still evolving, and there's no penalty for switching later. If your boiler is over 12 to 15 years old or needs increasingly frequent repairs, planning the heat pump switch proactively, rather than reactively when the boiler fails in January, gives you time to get proper quotes and a heat-loss survey instead of an emergency like-for-like replacement under pressure.
There's a middle option too: some homeowners get the heat-loss survey and quotes done now, while the boiler still works, then hold the quote for a few months and install once the timing suits (a quiet period at work, before a cold snap, once savings are in place). Most MCS-certified installers are used to this and will requote if prices or the BUS grant amount change materially before you're ready to proceed.
Whichever path you choose, make the decision deliberately rather than by default. A boiler swap under emergency pressure in January rarely leaves room to compare heat pump quotes properly, so if you're on the fence, getting heat pump quotes now, even with no immediate plan to install, costs nothing and gives you real numbers to weigh against a future emergency gas boiler replacement. Keep the quote and survey results on file, most are valid for several months and give you a genuine head start if your boiler does fail unexpectedly, rather than scrambling for a same-week like-for-like swap with no time to weigh the alternative properly.
Ready to get heat pump quotes? Start by finding installers in your region, then read our questions to ask guide.
Sources
- Ofgem, energy price cap (accessed 18 May 2026)
- Climate Change Committee, Sixth Carbon Budget heat strategy (accessed 18 May 2026)
- gov.uk, Future Homes Standard 2025 (accessed 18 May 2026)
- Nesta, heat pump economic case (accessed 18 May 2026)