Defaults last checked: October 29, 2026. Results are estimates.
A heat pump doesn’t burn anything. It moves heat, so each kWh of electricity delivers several kWh of warmth. Electricity usually costs more per kWh than gas or oil, though. Whether a heat pump is cheaper to run comes down to one comparison: is its seasonal efficiency high enough to make up for the price gap? This calculator gives you that break-even figure along with the running costs.
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How to use it
- Pick your country and current fuel, gas or oil.
- Enter how much fuel you buy in a year, in kWh. UK gas bills show kWh. US bills often show therms (1 therm ≈ 29.3 kWh) or hundreds of cubic feet. For heating oil, 1 US gallon is about 40.6 kWh, based on the EIA’s 138,500 Btu per gallon. For the UK we start with Ofgem’s typical medium gas use of 9,500 kWh a year.
- Check the boiler efficiency. We use ENERGY STAR’s minimum for certified boilers: 90% for gas, 87% for oil. An older non-condensing boiler can be well below that, which makes a heat pump look better.
- Set the heat pump’s SCOP. The default of 2.80 is the median measured across 291 air source heat pumps in the UK’s Electrification of Heat trial. Your installer’s design figure may be higher, but measured results are a useful reality check.
- Add the installed price and any grant. In England and Wales, the Boiler Upgrade Scheme is prefilled at £7,500.
The formula
- Heat your home uses = fuel bought × boiler efficiency
- Boiler running cost = fuel bought × fuel price per kWh
- Heat pump electricity = heat ÷ SCOP
- Heat pump running cost = heat pump electricity × electricity price
- Break-even SCOP = electricity price ÷ (fuel price ÷ boiler efficiency)
- Payback = (installed price − grant) ÷ yearly saving
The break-even SCOP is the most useful number here. If your heat pump will beat it, it’s cheaper to run than the boiler. If it won’t, it isn’t, at least on a standard tariff.
Worked example 1: UK gas, winter 2026
With Ofgem’s October–December 2026 cap rates (electricity 26.32p, gas 7.97p per kWh) and a 90% efficient boiler, the break-even SCOP is 26.32 ÷ (7.97 ÷ 0.90) ≈ 2.97.
For 9,500 kWh of gas a year:
- Boiler: £757
- Heat pump at SCOP 2.8: 3,054 kWh = £804 (about £47 more)
- Heat pump at SCOP 3.5: 2,443 kWh = £643 (about £114 less)
Disconnecting from gas also saves the gas standing charge, 29.68p a day under the current cap (about £108 a year). We explain how tariffs and flow temperatures shift these numbers in heat pump running costs vs gas.
Worked example 2: US heating oil
At the EIA’s residential heating oil price of $6.233 a gallon (week of October 26, 2026), oil costs about 15.4 cents per kWh. With an 87% boiler and US electricity at 18.16 cents, the break-even SCOP is only about 1.03. Almost any working heat pump beats it.
A home burning 700 gallons a year spends about $4,363 on oil. At SCOP 2.8, a heat pump would use roughly 8,830 kWh, or about $1,603, a saving of around $2,760 a year. For US natural gas, using the EIA’s 2025 average residential price, break-even is much higher, at about 3.24. That’s why the case for switching from gas is harder in many states.
What the result doesn’t tell you
- Standing charges aren’t included (see the gas example above).
- Real-world SCOP depends on flow temperature, radiator sizing and how the system is set up. Two identical heat pumps can perform very differently.
- Heat pump tariffs with cheaper hours can cut running costs noticeably. Enter a blended price if you have one.
- Hot water is included only if it’s in the fuel figure you enter.
Compare supplier tariffs
In the UK and Australia, pick your region and the calculator ranks the tariffs we could verify on each supplier’s own price sheet, with the source and check date on every card. “Use this rate” copies a unit rate into the calculator. In London, Flexible Octopus is 26.60p/kWh plus 41.39p/day; British Gas, EDF and E.ON Next are 26.60p/kWh plus 42.91p/day. The price cap keeps standard tariffs close, so near-ties are normal.
FAQ
What SCOP should I expect?
The UK trial median was 2.80, with the middle half of homes between 2.53 and 3.09. Well-designed systems with low flow temperatures do better. Ask your installer for the design SCOP at your flow temperature, and use a lower number to see the downside.
Is the Boiler Upgrade Scheme grant included automatically?
For the UK, yes: £7,500 for an air or ground source heat pump in England and Wales. Until March 2027 there’s an extra £1,500 if your home is heated by oil or LPG and has no mains gas. Our Boiler Upgrade Scheme guide covers who qualifies.
Why does oil make such a difference?
Oil currently costs much more per kWh than mains gas, so the break-even SCOP is low and a heat pump saves more.
Do I need better insulation first?
Not always, but reducing heat loss lowers the size of the heat pump you need and helps it run at lower flow temperatures. Start with the cheap measures in our draft-proofing guide.
Related
- Heat pump running costs vs a gas boiler (UK)
- Air-to-air vs air-to-water heat pumps
- Smart thermostats for heat pumps
- Loft and attic insulation: cost and savings