The trade-off in one paragraph
A heat pump moves heat from the outside air rather than making it, so across a year a well-designed system delivers roughly three units of heat for each unit of electricity it uses. A modern gas boiler delivers a little under one unit of heat per unit of gas. But a unit of electricity costs several times more than a unit of gas, so the efficiency advantage and the fuel price disadvantage largely cancel out.
That is why most homes land somewhere near parity with a good gas boiler on annual running cost, and why the interesting question is not the national average but which side of parity your setup falls. The three levers are the tariff you are on, the temperature the system runs at, and how well the pump was sized in the first place.
The levers that tip it your way
Tariffs first: heat-pump-specific electricity tariffs with cheap off-peak windows are the single biggest lever, because they attack the expensive half of the trade-off directly. Running temperature second: a heat pump run at a low, steady flow temperature is meaningfully more efficient than one driven hard in bursts like a boiler, which is a habit change as much as a settings change.
Sizing underpins both, which is why the room-by-room heat loss survey matters as much for your bills as for the price of the installation. An oversized unit switches on and off constantly and never settles into its efficient rhythm. Whether your radiators support a low flow temperature is part of the same calculation, covered in radiators and insulation.
Compare heat pump quotes
Up to three trusted, MCS-certified installers quote for the work, grant applied where you qualify. Free, no obligation.
Compare heat pump quotesComparing it with keeping the boiler
Against a gas boiler the running costs are usually close, so the decision tends to rest on the £7,500 grant cutting the upfront gap, on getting off gas, and on the standing charge arithmetic of dropping to a single fuel. Against oil, LPG or direct electric heating the sums are friendlier still, and off-grid homes get an extra £1,500 on the grant until March 2027.
If you are weighing the whole decision rather than just the fuel bill, heat pump or gas boiler walks through it. And because running cost depends so heavily on design, quotes are worth comparing on proposed flow temperature and heat loss figures, not just price: get quotes from MCS-certified installers and ask each for both numbers.
Compare heat pump quotes
Up to three trusted, MCS-certified installers quote for the work, grant applied where you qualify. Free, no obligation.
Compare heat pump quotes