If your boiler is on its last legs, or a renovation is forcing a heating decision for the next decade and a half, you’ve probably noticed the heat pump vs gas boiler debate has got noisier, not clearer. One week it’s a £15,000 disaster that won’t heat your house in January. The next it’s the future and you’re a climate vandal for fitting another combi. Both takes are nonsense.
This is the version that tries to give you a straight answer. What each system costs in 2026, what it costs to run, which homes each one actually suits, and where the trade-offs sit. By the end you should know which is the right call. Both are still legitimate answers.
How each system actually heats your home
A gas boiler burns mains gas, heats water in a heat exchanger, and pumps that hot water around your radiators and through your taps. The water it sends to radiators is typically 60–75°C, hot enough that a small radiator can chuck out a lot of heat in a short burst.
An air source heat pump works differently. It doesn’t make heat. It moves it. The unit outside cycles refrigerant through a compressor, evaporator and condenser. It pulls low-grade heat out of the outside air, upgrades it via the refrigerant cycle, and transfers that heat into water that gets pumped to your radiators or underfloor heating.
The catch is the output temperature. A heat pump runs most efficiently at 35°C to 50°C flow temperatures. To deliver the same amount of heat into a room at a lower temperature, you need larger radiators, more of them, or underfloor heating. Heat pumps also run for longer periods at lower output rather than blasting on and off the way a boiler does. The house ends up at a more constant temperature.
For the deeper dive on the mechanics, Heat Pump Sizing for UK Homes covers the kW calculations and radiator implications properly.
Upfront cost in 2026
A like-for-like combi boiler replacement in 2026 typically runs £2,500 to £4,500 fitted. A more involved swap (combi to system, relocating the boiler, upgrading flues) can push £5,000–£6,000. Bigger homes might end up at £4,500–£5,500 for a quality heat-only or system boiler with a new cylinder.
Heat pumps are a wider spread. The honest range for an air source install in 2026, before any grant, is £8,000 at the cheap end up to £15,000 or more for a larger home that needs radiator upgrades, a new cylinder, and chunky pipework changes. Most three- and four-bedroom homes get quotes in the £10,000 to £13,000 zone.
That’s before the Boiler Upgrade Scheme takes a chunk off. The BUS currently pays £7,500 toward an air source heat pump for owner-occupiers and private landlords in England and Wales. From July 2026 there’s a temporary uplift to £9,000 for homes currently on oil or LPG, running until March 2027. Scotland has Home Energy Scotland grants and interest-free loans. Wales has additional Nest support for eligible households.
Apply the £7,500 to the typical install range and the net cost lands between £1,000 and £8,000 for most homes, with the middle of the bell curve around £3,000 to £6,000. For a deeper breakdown of what drives quotes up or down, the Heat Pump Cost Guide goes into the line items.
Your installer applies for the grant on your behalf. It’s deducted from your quote upfront, you pay the net figure. You need an MCS-certified installer. The scheme is funded through to March 2028. Heat pumps are also zero-rated for VAT until March 2027.
Running costs at current prices
Under the Ofgem price cap for April to June 2026, average Direct Debit unit rates are:
- Gas: 5.74p per kWh
- Electricity: 24.67p per kWh
Electricity at around 4.3 times the price of gas is the central tension in this entire conversation. A heat pump uses electricity. If it were only as efficient as a gas boiler, running costs would be a disaster. It’s not, and they’re not, but the gap is narrower than the marketing suggests. The tariff you sit on after install is the difference between winning and breaking even.
Worked comparison: a typical UK home
Take a three- to four-bedroom semi with a heat demand of 12,000 kWh of useful heat per year. That’s roughly average for an English house.
Gas boiler at 90% efficiency. To deliver 12,000 kWh of heat, the boiler burns about 13,333 kWh of gas. At 5.74p per kWh, that’s roughly £765 per year before standing charges.
Heat pump at SCOP 3.5 on the standard price cap. The Seasonal Coefficient of Performance is the heat pump’s real-world efficiency averaged over the year. At SCOP 3.5, delivering 12,000 kWh of heat takes about 3,429 kWh of electricity. At 24.67p per kWh, that’s roughly £846 per year. On a standard variable tariff with no load shifting, the heat pump is slightly more expensive to run than the gas boiler. Not by much, but it’s there. That’s the bit nobody mentions when they tell you heat pumps slash your bills.
Heat pump at SCOP 3.5 on Cosy Octopus. Cosy Octopus is a three-rate time-of-use tariff for heat pump homes. From April to June 2026 it has off-peak rates of around 14.53p per kWh during three daily windows (4–7am, 1–4pm, 10pm–midnight), a peak rate of 51.68p from 4–7pm, and a standard rate of 33.28p the rest of the day.
Shift roughly 70% of heat pump consumption into the off-peak windows and the blended electricity cost drops to around 19–21p per kWh. At a blended 20p with SCOP 3.5, that 3,429 kWh costs about £686 per year. Cheaper than the gas boiler. Push the heat pump up to SCOP 4.0 in a well-insulated home and the same heat costs around £600.
Octopus’s own fleet data reports that 93% of their Cosy heat pump customers heat their home more cheaply than they would with a gas boiler. Take that with the usual marketing pinch, but the underlying maths checks out for most reasonably installed systems.
The honest summary
- On a standard variable tariff, a heat pump runs roughly the same cost as a gas boiler.
- On a heat pump tariff like Cosy Octopus, EDF Heat Pump Tracker or British Gas Heat Power, a well-installed heat pump usually beats gas by £150–£400 a year.
- A poorly installed heat pump at high flow temperatures (SCOP 2.5 or worse) will lose to gas every time. This is the single biggest variable.
EDF’s Heat Pump Tracker is worth a mention for households who can’t easily shift load away from evening peak. It never charges above the price cap and gives six hours of discounted electricity daily, but the headline savings are smaller than Cosy. OVO’s Heat Pump Plus was withdrawn in February 2026.
For more on tariff choices, Energy Tariffs Explained and Best UK Energy Suppliers both go further. For heat pump installer quotes through a referral process, [Affiliate Link].
Summary comparison table
| Factor | Gas Boiler | Air Source Heat Pump |
|---|---|---|
| Typical installed cost (2026) | £2,500–£5,500 | £8,000–£15,000 |
| Net cost after BUS grant | £2,500–£5,500 (no grant) | £1,000–£8,000 (£7,500 off) |
| Typical annual running cost | £700–£800 | £600–£850 depending on tariff and SCOP |
| Expected lifespan | 10–15 years | 15–20 years |
| Space required | Kitchen cupboard | External unit plus indoor cylinder |
| Noise | Quiet, mostly inside | 35–45 dB at 1m outside |
| Suitability for poorly insulated homes | Works regardless | Needs fabric upgrades first |
| Suitability for well insulated homes | Fine | Where heat pumps shine |
| Ease of install | A day or two | Two to five days |
| Ongoing maintenance | £80–£150 | £150–£300 |
Is your home suitable for a heat pump?
This section does the real work. A heat pump in the wrong house is genuinely a bad outcome. In the right house it’s great. The trick is honest diagnosis.
Insulation standard. EPC C or above is the comfortable zone. Below that and you’re either looking at fabric upgrades first or accepting higher running costs because the pump will work harder. If you’re at EPC E or F with single glazing and solid uninsulated walls, an honest installer will tell you to do the fabric work first. The ones who’ll quote you a 16kW pump and a chunky bill instead are the ones to avoid.
Radiator sizing. Because heat pumps run at 35–50°C flow temperatures, you usually need bigger radiators, more of them, or underfloor heating. Some of your existing radiators will be fine. Some will need upgrading to double-panel double-convector versions.
Hot water cylinder. This is the catch for combi households. A heat pump can’t do instant hot water. You need a cylinder, typically 180–250 litres for a family home. That cylinder needs space, usually an airing cupboard or hallway nook.
Outdoor space. The external unit needs somewhere to live. Permitted development covers most installations, but there are caveats around conservation areas, listed buildings, and proximity to boundaries.
Hot water demand. Big households with multiple showers running at once can find a cylinder undersized if it’s been spec’d to the bone. Talk this through with your installer.
If your home doesn’t comfortably tick the insulation box, EPC Ratings Explained is a useful starting point.
The cold weather question
Heat pumps work in UK winters. Modern air source units operate down to roughly -15°C to -20°C, and the UK rarely sees colder than -5°C to -8°C even in a proper cold snap. Norway, Sweden and Finland are full of heat pumps. So is Scotland.
Efficiency does drop as it gets colder. A heat pump that hits SCOP 3.5 averaged over the year might run at COP 2.5 or 2.0 on a freezing morning. That means a slightly more expensive cold week. It does not mean the house gets cold.
Real-world UK installs rarely hit the lab figures. The Energy Saving Trust’s field trial of 742 UK installations found an average SCOP of 2.9, with well-insulated homes averaging 3.4 and the bottom quartile averaging 2.3. The heatpumpmonitor.org fleet reports an average closer to 3.87 (January 2026), which skews toward enthusiast-quality installs. Aim for SCOP 3.5+ as a realistic target. Below 3.0 and the install is worth interrogating.
The Boiler Upgrade Scheme
England and Wales:
- £7,500 toward an air source or ground source heat pump
- £2,500 toward an air-to-air heat pump (rooms-only, no hot water)
- £5,000 toward a biomass boiler (rural off-grid only)
- £2,500 toward a heat battery
- £9,000 uplift for oil or LPG homes, July 2026 to March 2027
Scotland: Home Energy Scotland offers grants of up to £7,500 plus optional interest-free loans of up to £7,500. Wales: The Nest scheme covers eligible low-income households.
Eligibility: Owner-occupier or private landlord, valid EPC less than 10 years old, no outstanding loft or cavity wall insulation recommendations, MCS-certified installer. The installer handles the application. The grant is deducted upfront. Funded through to March 2028. Grant values have changed before and could change again. Check current value before signing anything.
Lifespan and the long view
Gas boilers typically last 10 to 15 years. Heat pumps typically last 15 to 20 years. Annual servicing is £80–£150 for a gas boiler and £150–£300 for a heat pump.
The proposed 2035 ban on new gas boiler installs has been effectively dropped under the current government’s Warm Homes Plan. There is no fixed phase-out date for replacement boilers in existing homes.
What is in place is the Clean Heat Market Mechanism, which started in April 2025. It puts a heat pump sales obligation on boiler manufacturers (6% of fossil fuel boiler sales in year one, rising to 8% from April 2026). Some manufacturers have added a small surcharge to boiler prices, others have absorbed it. The net effect on retail prices in 2026 is modest.
The wider direction of travel is harder to argue with. Electricity is decarbonising. Gas prices are unlikely to fall much in real terms over a 10–15 year horizon. The 4.3:1 gap between gas and electricity unit prices is what’s holding heat pumps back, and there’s regular discussion about rebalancing energy levies to narrow it. If you’re picking a heating system in 2026 that will still be running in 2040, the trajectory matters.
When a gas boiler is still the right answer
A working gas boiler in 2026 is not a sin.
Very poorly insulated homes. EPC E or worse with no budget to upgrade the fabric. Fit a quality gas boiler. Use the saved money toward insulation.
Moving in the next couple of years. Payback against the gas running cost difference takes years even on a heat pump tariff. If you’re leaving, you won’t see it.
Tight upfront cashflow. Even after the grant, a heat pump install is often £2,000–£6,000 more than a like-for-like boiler swap.
Period properties with planning restrictions. Conservation areas, listed buildings, and homes close to boundaries can make the external unit awkward or impossible.
Very high hot water demand and no cylinder space. A four-bathroom house with no airing cupboard is a heat pump installer’s headache.
If any of these apply, fit the boiler, get a good one, get the warranty, move on.
When a heat pump is clearly the right answer
Well-insulated homes. Newer builds, post-2010 stock, anything retrofitted to a decent standard. EPC C or above.
Staying long-term. The 15–20 year lifespan combined with the running cost advantage on a smart tariff stacks up over time.
Space for a cylinder and an outdoor unit. Most homes have it.
Willing to engage with a time-of-use tariff. This is the bit that tips the maths. Use the heat pump’s controls and your hot water cylinder as a thermal battery and the running costs work. Set it and forget it on a standard variable and the financial case is weaker.
Solar PV installed or planned. A heat pump plus solar plus a battery is a strong combination. See Are Solar Panels Worth It in the UK? for the solar side.
Doing a full renovation. Pipework’s out, floors are up, radiators are coming off. This is the cheapest moment to fit a heat pump.
How to make the decision
- Get an EPC and an honest insulation review. If your EPC is older than five years, refresh it. A proper retrofit assessment (£200–£500) is better if you can afford one.
- Get at least three MCS-certified heat pump quotes. Quotes for the same property can vary by £4,000–£6,000. Use the MCS Certified database.
- Get one or two gas boiler quotes for reference. You need to know what you’re walking away from.
- Apply the current BUS grant to the heat pump figures. Query any “BUS application contingent” caveat that pushes risk onto you.
- Run a realistic running cost comparison. Pull your actual annual kWh of gas from your bills. Apply 90% efficiency. Run that useful-heat figure through both a current gas tariff and a heat pump tariff using a realistic SCOP of 3.0–3.5. Don’t use the installer’s optimistic figure.
- Factor in lifespan and fuel price trajectory. 15 years for a boiler, 20 for a heat pump. Use a range, not a point estimate.
- Decide on the total picture, not just upfront cost.
Common pitfalls
- Assuming heat pump quotes are uniform. The same install can come in at £9,000 from one installer and £14,500 from another.
- Installers who undersize the pump or skip radiator upgrades to win the job. The SCOP tanks, the bills are higher than expected.
- Skipping insulation work and blaming the heat pump for high bills. Loft and cavity work pays back faster than a heat pump install.
- Comparing heat pump running costs on a standard variable tariff. The tariff is part of the system.
- Going for the cheapest gas boiler swap and ending up with a 7kW combi servicing a 12kW house.
- Accepting “we don’t think your house is suitable” from one installer as final. Get a second opinion.
FAQ
Is a heat pump really cheaper to run than a gas boiler? Usually yes, but only on a dedicated heat pump tariff and with a decent SCOP. On a standard variable with a mediocre install, it can be slightly more expensive.
Do I need new radiators? Usually a few. Some will be fine, some will need upgrading to bigger panels.
Will a heat pump work in an old house? It depends on insulation. A solid-wall Victorian terrace with single glazing is a hard sell without fabric upgrades first.
How much is the BUS worth in 2026? £7,500 for a standard air source heat pump in England and Wales. £9,000 for off-grid homes on oil or LPG between July 2026 and March 2027.
Are heat pumps noisy? The outdoor unit makes a low hum, 35–45 dB at one metre, similar to a quiet fridge.
Can I keep my gas boiler as backup? Hybrid systems exist but don’t qualify for the BUS grant. Most people who switch take the gas out entirely and drop the standing charge.
Will gas boilers actually be banned? The proposed 2035 ban has been dropped under the Warm Homes Plan. No firm phase-out date for replacement boilers.
How long does installation take? Two to five days for a heat pump. A single day for a combi boiler swap.
Conclusion
There’s no universal answer. The right call depends on your house, your insulation, your budget, and how long you’re staying.
Broken boiler, limited budget, poorly insulated home. Fit a quality gas boiler now. Sort your insulation over the next two or three years. Revisit when the next boiler dies.
Planning a renovation. Strongly consider the heat pump. The disruptive work is already happening, the grant brings the net cost down, and a 20-year horizon makes the running cost maths work.
Well-insulated home, staying long term, comfortable cashflow. The heat pump is probably the right call. Get three MCS quotes, run the numbers on a heat pump tariff, commit if the SCOP target looks realistic.
Poorly insulated home with no insulation plans. Stick with gas. A heat pump in a leaky house is the worst of both worlds.
For installer quotes through a verified panel, [Affiliate Link]. For deeper background on heat pump performance and sizing, Heat Pumps is the pillar guide. For the wider energy efficiency picture, How to Reduce Your Energy Bills is worth a read.
Whichever way you go, do it on the numbers. They’re the only honest answer in this debate.