Whether a heat pump is cheaper to run than a gas boiler is one of the most asked and most muddled questions in home energy, and the honest answer is that it depends on two numbers: how efficiently the heat pump runs, and the gap between what you pay for electricity and what you pay for gas. Get both in your favour and a heat pump is clearly cheaper; get them against you and it can cost about the same or more. This guide works out the real figures rather than the slogans.
The short answer. A gas boiler is roughly 90 per cent efficient, so a unit of gas at the current price-cap rate of 7.33p gives heat at around 8.1p per kWh. A heat pump delivers about three to four units of heat per unit of electricity, so at the 26.11p standard electricity rate it gives heat at roughly 6.5p to 8.7p per kWh, depending on its efficiency. That means a good heat pump now edges ahead of gas even on a standard tariff, while a poorly performing one roughly matches it. On a dedicated heat-pump electricity tariff the heat pump wins comfortably. The deciding factor is the price gap between electricity and gas, not the technology.
The two numbers that decide it
A gas boiler and a heat pump make heat in completely different ways, and comparing them fairly means reducing both to the same thing: the cost of a unit of useful heat delivered into your home. For a gas boiler that depends on the price of gas and the boiler's efficiency, which for a modern condensing boiler running well is around 90 per cent, so a little of the gas you pay for is lost. For a heat pump it depends on the price of electricity and the pump's efficiency, measured as its coefficient of performance or, over a year, its seasonal figure. Crucially a heat pump does not burn its electricity for heat; it uses it to move heat from outside into the house, so it delivers several units of heat for each unit of electricity, as the heat pumps explained guide describes. A good system returns three to four units of heat per unit of power.
Cost per unit of heat, worked out
Put real prices in and the comparison comes alive. The figures below use the current Ofgem price-cap unit rates for 1 July to 30 September 2026, gas at 7.33p per kWh and electricity at 26.11p (direct debit, the England, Scotland and Wales average), plus a separate lower rate for a dedicated heat-pump tariff. The heat pump rows show different efficiencies, because a well-designed system in a well-insulated home achieves a higher figure than a poorly set one.
| Heating | Assumption | Cost per kWh of heat |
|---|---|---|
| Gas boiler | 7.33p gas, 90% efficient | ~8.1p |
| Heat pump, standard rate | 26.11p electricity, efficiency 3.0 | ~8.7p |
| Heat pump, standard rate | 26.11p electricity, efficiency 3.5 | ~7.5p |
| Heat pump, standard rate | 26.11p electricity, efficiency 4.0 | ~6.5p |
| Heat pump, heat-pump tariff | 15p electricity, efficiency 3.5 | ~4.3p |
Gas 7.33p and electricity 26.11p are the Ofgem price-cap unit rates for 1 July to 30 September 2026 (direct debit); both vary by region and tariff, so check your own bill. The heat-pump tariff row uses an example 15p rate typical of dedicated heat-pump deals. Standing charges are separate, and going all-electric removes the daily gas standing charge, about 29p a day under the same cap.
Why it is close, and which way it now leans
The table shows the heart of the matter. On a standard tariff, a heat pump running at a typical real-world efficiency of around 3.5 delivers heat at about 7.5p per kWh, a little under the gas boiler's 8.1p, so a well-performing pump now edges ahead of gas even before any special tariff. The reason it stays close at all is that electricity in Britain costs about three and a half times as much as gas per unit, while a good heat pump is roughly three to four times as efficient as a boiler at turning what you pay for into heat. Those two ratios nearly cancel, which is why the standard-tariff rows sit close to the gas figure rather than far below it. It also means the result is sensitive: a pump achieving a high efficiency comes out clearly cheaper, while one running poorly, in a draughty house or set up to run hot, can slip back to roughly level with or above gas. The fabric of the home and the quality of the installation matter as much as the box on the wall.
Why the tariff changes everything
The bottom row is where the heat pump pulls clear. Because it runs on electricity, a heat pump can use a dedicated heat-pump or time-of-use tariff, where the unit rate is well below the standard cap. Drop the electricity price and the heat pump's cost per unit of heat drops with it, comfortably below gas, while the gas boiler has no such lever. This is the same lesson the EV charging guides keep returning to: once a thing runs on electricity, the tariff you put it on becomes the biggest cost decision you make. A heat pump on the right electricity tariff is clearly cheaper to run than a gas boiler; the same heat pump on a flat standard rate is cheaper only by a little at best, and roughly level if it runs poorly.
What it means for a year's heating
A typical home needs very roughly 11,000 to 12,000 kWh of heat a year. At the per-unit figures above, that is around 900 to 980 pounds of gas through a boiler, a little less for a heat pump on a standard rate at a good efficiency, and roughly 500 pounds for a heat pump on a good heat-pump tariff, plus or minus a great deal depending on your home, your habits and your rates. Set against the boiler you also save its servicing and lose the gas standing charge, about 29p a day or some 105 pounds a year, if you go fully electric. These are illustrative, not a quote: your own annual heat demand and unit rates move the answer a lot, so treat the per-unit cost as the reliable comparison and scale it to your own usage.
Getting a heat pump into the cheaper column
Since the result is decided at the margin, the things that tip it are worth doing. Insulate and draught-proof first, because a warmer, tighter home lets the heat pump run at a lower flow temperature, which is exactly where it is most efficient, so the insulation and draught-proofing basics pay double. Size and set the system properly, running it steady and gentle rather than in hot blasts, the opposite of how many people run a boiler, as the flow temperature guide explains for boilers and which matters even more for a pump. And get onto a heat-pump electricity tariff. Do all three and a heat pump moves from break-even to clearly cheaper; skip them and it struggles to beat the boiler it replaced.
The bottom line
A heat pump is not automatically cheaper to run than a gas boiler, and anyone who tells you it always is, or never is, is skipping the arithmetic. On a standard tariff the two are close, because electricity costs about three and a half times what gas does while a good heat pump is three to four times as efficient, so the ratios nearly cancel and a well-set pump edges ahead. The heat pump wins clearly when it runs efficiently in a well-insulated home on a dedicated electricity tariff, and only slips behind when those are missing. Do the fabric, set it up to run gently, and put it on the right tariff, and the running cost lands firmly in its favour.