A cold snap arrives, the boiler clears its throat, and a quote for a replacement lands on the kitchen table. Somewhere between that moment and signing on the dotted line, most homeowners ask the same question: stay with gas, or switch to a heat pump? Both systems keep a house warm, but they work in very different ways, and the better choice depends less on fashion than on your property, your budget and how you like to live. What follows is the comparison worth having before anyone visits to quote.
A gas boiler burns fuel. That flame heats water, the water travels to radiators or underfloor loops, and the boiler then switches off until the thermostat asks for more. It is a burst of high-temperature heat, which is why a boiler can take a chilly living room from 16°C to 21°C in under an hour.
A heat pump does not create heat so much as move it. Using electricity and a refrigerant cycle, it pulls warmth out of the outside air, or the ground, and pushes it into your home. The useful measure is efficiency: for every unit of electricity it uses, a well-installed system delivers several units of heat. That is why heat pumps run best at lower flow temperatures, typically 35–45°C, and prefer to run long and gently rather than in short, hot bursts.
Expect a heat pump to cost noticeably more than a straight boiler swap. There is more equipment — an outdoor unit, an indoor unit, usually a hot water cylinder — and often more labour, because radiators may need upsizing and pipework may need altering. A like-for-like gas boiler replacement is a simpler purchase and usually the cheaper one on day one.
That gap can narrow considerably through grants and incentive schemes, which vary by country, region and sometimes by postcode, and which change often. Check the official government or regional energy portal rather than relying on a salesperson's summary, and confirm the current rules before you commit. Ask what a heat pump quote should itemise:
This is where the comparison gets less tidy. In most markets, electricity costs more per unit than gas. A heat pump therefore has to be roughly three times more efficient than a boiler to match it on running costs, and a well-designed, well-configured system can reach that territory. A poorly designed one, squeezed into a draughty house with undersized radiators, will not.
Four things move the numbers more than the brand on the outdoor unit:
Ask each installer for a predicted annual consumption figure in kilowatt hours, then apply your own tariff to it. A price alone tells you very little. For anything involving tariffs, grants or tax treatment, take advice from a qualified energy adviser.
Heat pump owners tend to describe the warmth as even rather than powerful. Rooms hold their temperature, floors lose their chill, and there is less of the swing between too hot and too cold that comes from a boiler cycling on and off. The trade-off is response time: turn the thermostat up three degrees and nothing dramatic happens for a while. Underfloor heating pairs beautifully with a heat pump for exactly this reason.
Boilers win on immediacy. A combi gives endless hot water at mains pressure, and high-temperature radiators heat a cold room fast, which suits households that come and go and want quick recovery. Radiators near a heat pump will usually be larger to give the same output at a lower temperature, so factor that into both the budget and the look of each room.
Rule of thumb: a heat pump rewards patience and good settings; a boiler rewards a well-sized unit and sensible thermostat schedules. Neither forgives a badly insulated room.
A boiler swap is usually a day or two of work with limited disruption. A heat pump installation typically takes longer, from a few days to over a week, and involves more trades. The outdoor unit needs space with proper clearance and a siting that will not annoy you or a neighbour once it is humming in January. The cylinder needs cupboard space, ideally indoors. The electrical supply needs checking early, because upgrades can add cost and delay.
If your home is small, well served by an existing modern boiler, short on outdoor space, or if the upfront budget simply is not there, replacing like for like is a defensible decision. A new condensing boiler running at a sensible temperature is far from wasteful. Where a heat pump looks marginal, a phased plan — insulation and draught-proofing first, heating system later — often gets a better result than rushing the swap.
Start with the fabric of the house, not the equipment. Spend an evening noting which rooms are cold, where draughts come from, and how the household actually uses hot water. Then get two or three quotes that include a heat loss calculation and a written performance estimate, not just a headline price. Ask each installer what flow temperature they expect to run at, and why.
If the numbers come out close, weigh the things a spreadsheet misses: the noise outside a bedroom window, the cupboard you lose to a cylinder, the comfort of steady heat, and how long you plan to stay. A heating system is a fifteen-year decision installed in a week. Give it the same attention you would give a kitchen, and the choice becomes much clearer.
Photo: stevepb / Pixabay
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