A heat pump is cheaper to run than a gas boiler when its efficiency (SCOP, typically 3 to 4) is higher than the ratio of your electricity price to your gas price. On a standard tariff that is close to a draw; on a heat pump tariff the heat pump wins. Upfront, a heat pump costs £8,000 to £15,000 for a 3 bed home before the £7,500 grant, against a few thousand pounds for a like for like boiler swap. Which is right for you depends on your house, your tariff and how long you plan to stay.
Key takeaways
- The running cost test: divide your electricity unit price by your gas unit price. If the heat pump SCOP is higher than that number, the heat pump is cheaper per unit of heat.
- At a SCOP of 3.5 and a typical price ratio of about 4 to 1, the two are roughly level. A well insulated house running at a SCOP of 4, or a heat pump tariff, tips it to the heat pump.
- Upfront: heat pump £8,000 to £15,000 for a 3 bed home before the £7,500 grant, 0% VAT; a like for like gas boiler swap is indicatively £2,000 to £4,000 at 20% VAT.
- Comfort is different, not worse: a heat pump runs for longer at a lower temperature, so rooms stay at a steady heat rather than cycling hot and cold.
- Gas still wins where the house is very leaky and will not be insulated, where there is no space for a cylinder or outdoor unit, or where the budget only stretches to a boiler.
- Insulating first improves the heat pump case on every line: smaller unit, fewer radiator changes, higher SCOP, lower bills.
Is a heat pump cheaper to run than a gas boiler?
Electricity costs more per kWh than gas, usually around four times more. A heat pump gets round that by moving heat rather than making it: over a year it delivers about 3 to 4 kWh of heat for every 1 kWh of electricity. That number is the SCOP (seasonal coefficient of performance). A gas boiler delivers about 0.85 to 0.9 kWh of heat per kWh of gas burned.
So the sum is simple. Take your electricity price per kWh and divide it by the heat pump SCOP. Take your gas price per kWh and divide it by the boiler efficiency. Whichever is lower is cheaper per unit of heat. Your annual heating bill is that figure multiplied by the heat your home needs, which insulation reduces for either system.
| System (illustrative prices, put in your own) | Sum | Cost per kWh of heat |
|---|---|---|
| Gas boiler, 85% efficient, gas at 6p | 6p ÷ 0.85 | About 7.1p |
| Heat pump, SCOP 3.0, electricity at 25p | 25p ÷ 3.0 | About 8.3p |
| Heat pump, SCOP 3.5, electricity at 25p | 25p ÷ 3.5 | About 7.1p |
| Heat pump, SCOP 4.0, electricity at 25p | 25p ÷ 4.0 | About 6.3p |
| Heat pump, SCOP 3.5, heat pump tariff with a lower unit rate | Lower rate ÷ 3.5 | Below gas |
The pence figures show the method; tariffs change every quarter, so run it with your own bill. If the gas meter is removed you stop paying the gas standing charge, and a heat pump tariff with a lower unit rate, which several suppliers now offer, makes the heat pump the clear winner for most insulated homes.
What does each cost to install?
| Gas boiler (like for like swap) | Air source heat pump | |
|---|---|---|
| Typical installed cost, 3 bed home | Indicatively £2,000 to £4,000 | £8,000 to £15,000 before the grant |
| Grant | None | £7,500 Boiler Upgrade Scheme, deducted by the MCS installer |
| VAT | 20% | 0% until 31 March 2027, then 5% |
| Net cost, 3 bed home | Indicatively £2,000 to £4,000 | £500 to £7,500 |
| What is included | Boiler, flue, controls | Unit, cylinder, radiator changes, pipework, controls, commissioning |
The gap is smaller than it looks once the grant and VAT are in, but it is still real: the heat pump is a whole system change, the boiler is a swap. The air source heat pump cost guide breaks the heat pump figure down line by line. Larger homes are £12,000 to £20,000 before the grant.
Does a heat pump feel different?
Yes, and most people prefer it once they are used to it. A gas boiler sends water round the radiators at 60 to 75°C in short bursts. A heat pump runs at 35 to 55°C for long periods, often all day in cold weather. Radiators feel warm rather than hot, and the house holds a steady temperature instead of swinging between too warm and too cool.
Three things follow. Radiators may need to be larger, because a cooler radiator needs more surface area for the same heat. Hot water comes from a cylinder rather than on demand. And the fabric matters more: a leaky house forces the heat pump to run hotter, which drags the SCOP down. See heat pumps in old houses.
How long does each last?
Indicatively, a heat pump lasts 15 to 20 years and a gas boiler 10 to 15, so a heat pump often outlasts one and a half boilers. Both need an annual service. A heat pump has no flame or flue, but the outdoor unit lives in the weather, so keep it clear of leaves and let air flow round it.
Carbon is the other long term line. Grid electricity is already lower carbon per kWh than gas, and it gets cleaner each year, so a heat pump's emissions fall over its life while a boiler's do not.
When is a gas boiler still the right call?
- The house is leaky and will stay that way. Solid walls, no loft top-up, single glazing and no plan to insulate. The heat pump would be oversized, run hot and cost more than gas. Insulate first or stay with gas.
- No space. No outdoor wall or garden for the unit, or no cupboard for a 150 to 250 litre cylinder. Common in flats and small terraces.
- Budget. If the boiler has failed in January and there is no money for radiators and a cylinder, a boiler now and a heat pump later is a reasonable plan.
- Selling within a year or two. The running cost saving is spread over years; a heat pump is a long term buy.
None of these are permanent. The most common reason gas still wins in a London terrace is the first one, and it is fixed by insulation. Our insulate before a heat pump guide sets out the order of works.
A four step way to decide
- Run the running cost sum with your own tariff. If the SCOP beats the price ratio, the heat pump is cheaper to run.
- Book a free heat loss survey. It tells you the heat loss of your home, which measures cut it, and what size unit you would need before and after insulation.
- Insulate the cheap and fast measures first: loft top-up, draught proofing, and floor where it is accessible. Solid walls if the survey says so.
- Get the heat pump quote with the grant deducted and compare it against a boiler swap over 15 years, not one.
Heat pumps are arranged and project-managed by Stay Warm and installed by accredited, MCS certified installers; the insulation is done by our own PAS 2030:2023 certified team. See the air source heat pump service page.
Frequently asked questions
Is a heat pump cheaper to run than gas in 2026?
It depends on your tariff and the SCOP. At a SCOP of 3.5 and electricity about four times the price of gas per kWh, the two are level. At a SCOP of 4, or on a heat pump tariff with a lower unit rate, the heat pump is cheaper. Insulation pushes the SCOP up.
How much more does a heat pump cost than a boiler?
A heat pump is £8,000 to £15,000 for a 3 bed home before the £7,500 grant, so £500 to £7,500 net, at 0% VAT. A like for like boiler swap is indicatively £2,000 to £4,000 at 20% VAT. The heat pump includes a cylinder, radiator changes and controls; the boiler swap does not.
Do heat pumps work in cold weather?
Yes. They are designed for outdoor temperatures well below freezing and are standard in colder countries. Efficiency drops on the coldest days, which is why the annual figure (SCOP) is the one to use rather than a single day.
Will my radiators work with a heat pump?
Some will, some will not. A heat pump runs cooler, so radiators need more surface area for the same heat. A heat loss survey works out which rooms need larger radiators. In a well insulated house it is often only two or three.
Can I keep my gas boiler as a backup?
A hybrid system with both is possible, but the Boiler Upgrade Scheme grant is for a heat pump that replaces the fossil fuel heating, so a hybrid does not qualify. Most homes do not need a backup once the system is sized correctly.