Interactive comparison
Heat pump vs. gas boiler: the real savings
Electricity costs several times more than gas, kilowatt-hour for kilowatt-hour — and a heat pump can still be cheaper to run. Here is the one number that decides which way it goes, and a calculator to plug in your own prices.
The cost of the same kilowatt-hour of heat — from a gas boiler, and from a heat pump with a COP of 3.5, at typical European prices.
Electricity is expensive. Across most of Europe it costs three to five times more per kilowatt-hour than natural gas. On that fact alone, swapping a gas boiler for a heat pump looks like a bad trade — a pricier fuel, bought with a much pricier machine.
But a kilowatt-hour of electricity and a kilowatt-hour of gas do not buy the same amount of heat. A condensing gas boiler turns about 90% of the gas it burns into heat. A heat pump, as the previous guide explains, delivers several kilowatt-hours of heat for every one it consumes. The real comparison is not the price of the fuel — it is the price of the heat that fuel produces.
Do that division and the two figures above — the price gap and the efficiency gap — start racing each other. Which one wins depends entirely on your own prices and your heat pump's real-world performance. Here is how to work it out for your home.
01Cost per kWh of heat, not per kWh of fuel
A gas price of €0.08 per kWh and an electricity price of €0.28 per kWh are not directly comparable — one heats a home at roughly 90% efficiency, the other at 250–450%. Divide each price by its efficiency and you get the number that actually matters: the cost of one kilowatt-hour of heat delivered into the room.
cost of heat = energy price ÷ efficiency. For a condensing boiler, efficiency is about 0.90. For a heat pump, "efficiency" is the coefficient of performance — COP — and it usually runs 2.5 to 4.5 rather than a fraction below 1. That is the whole trick: a heat pump's COP can sit well above 100%, because it moves existing heat rather than creating it from fuel.
A cheaper fuel does not always mean cheaper heat. What matters is the fuel price divided by how much of it becomes warmth.
02Do the math for your own home
Enter your own gas price, electricity price, and the COP your heat pump actually achieves — not the number on the box, the one it delivers in your climate with your radiators. The chart below shows exactly where that leaves you.
Cost per kWh of heat delivered.
03Beyond the running cost
Running cost is only half the sum. A heat pump costs several times more to install than a gas boiler — often €8,000–€18,000 fitted, against €3,000–€6,000 for a boiler, before any subsidy. That gap has to be paid back out of the running-cost savings above, and at a modest 10–20% saving a year, payback can take a decade or more without help.
Most European countries subsidise heat pumps specifically, sometimes covering 30–50% of the installed cost — the figures change often enough that it is worth checking your national or regional programme directly rather than trusting a fixed number here. A subsidy is usually what turns a marginal running-cost saving into a clearly good financial decision.
A common middle path is a hybrid (bivalent) system: keep the old gas boiler as backup, let the heat pump handle the mild majority of the season when its COP is high, and let the boiler take over only on the coldest days, when the heat pump's advantage shrinks.
04Where the comparison bends
The same two prices can favour either side depending on details specific to your home:
- Insulation. A well-insulated home needs a lower flow temperature, which raises the heat pump's COP directly — the single biggest lever you control.
- Emitters. Underfloor heating or oversized radiators let the heat pump run at a lower, cheaper temperature than small old radiators do.
- Heat-pump electricity tariffs. Some countries and utilities offer a separate, cheaper heat-pump or night tariff — that alone can shift the whole comparison.
- Climate. Colder climates lower air-source COP exactly when heating demand is highest; ground-source systems are far less exposed to this.
Favours the heat pump
Good insulation, underfloor heating or large radiators, a heat-pump electricity tariff, a mild climate, a national subsidy.
Favours the gas boiler
Poor insulation, small old radiators, standard electricity pricing, a cold climate, no subsidy available.
05The short version
- Compare COP to your boiler's efficiency (about 90%), not to 100%.
- Cost of heat is price divided by efficiency — always divide before you compare fuels.
- At typical European prices, a heat pump with a COP above roughly 3.5–4 usually already wins on running cost.
- Installation cost is the bigger hurdle than running cost; a subsidy usually decides the payback period.
- Insulation and low-temperature emitters raise your real COP more than any amount of tariff-shopping.
More explainers
How a heat pump works
The physics behind the COP number used in this calculator — the refrigerant loop, step by step, with an interactive diagram.
03How solar panels work
The physics of turning sunlight into electricity, plus a calculator for how much of a heat pump's electricity your roof could cover.
Common questions
Is a heat pump really cheaper to run than gas?
Usually, once you account for efficiency rather than raw fuel price — but the margin depends heavily on your local electricity-to-gas price ratio and the COP you actually achieve. Use the calculator above with your own numbers.
How long does a heat pump take to pay for itself?
Purely from running-cost savings, often 8–15 years without a subsidy, and considerably less with one — subsidies covering 30–50% of installed cost are common across Europe.
Can I keep my gas boiler as a backup?
Yes — this is a common "hybrid" or "bivalent" setup: the heat pump covers most of the season, and the boiler switches in automatically on the coldest days. It also reduces the size and cost of the heat pump you need.
Does a heat pump save money even with expensive electricity?
It depends on the exact ratio. As a rule of thumb, once electricity costs about four times the price of gas per kWh, you need a COP above roughly 4.4 to still come out ahead — achievable, but not guaranteed with air-source systems in cold climates.
Do I need to upgrade my radiators?
Not always, but it helps. Underfloor heating or larger radiators let the heat pump run at a lower water temperature, which is the single biggest factor in its real-world COP.
Is this comparison different for hot water?
Domestic hot water is heated to a higher temperature than space heating, which lowers a heat pump's COP for that portion of its use — still normally cheaper than resistance heating, but usually less favourable than the space-heating comparison above.