Air Source Heat Pump vs Gas Boiler: UK Comparison (2026)

An air source heat pump works on the same principle as a refrigerator, but in reverse. Instead of extracting heat from inside a box and pumping it out, it extracts heat from the outdoor air and uses it to heat the water that feeds your radiators, underfloor heating and hot water cylinder.

The system uses a compressor and a refrigerant to absorb heat energy from outside air, even on cold days. That heat is concentrated by the compressor and transferred into your heating circuit. Because the system is moving heat rather than generating it, it delivers far more heat than the electricity it consumes.

The key metric is the SCOP (Seasonal Coefficient of Performance). A SCOP of 4 means that across a year, the heat pump delivers 4kWh of heat for every 1kWh of electricity consumed. Good modern units achieve SCOPs of 3.8-4.5. A gas boiler, by contrast, burns fuel directly: it can never deliver more heat than the energy in the gas, and in practice delivers slightly less once flue losses are counted.

The standard UK product is the air-to-water heat pump: one outdoor unit, connected to your wet central heating system and a hot water cylinder. It replaces the gas boiler entirely, heating and hot water both. That distinction matters for the grant: the £7,500 Boiler Upgrade Scheme applies to air-to-water and ground source systems, not to air-to-air units that only blow warm air.

Around 85% of homes in Great Britain are on mains gas, and the gas boiler is the incumbent. There are two main types:

Combi (combination) boilers heat your radiators and produce hot water on demand as it flows through the unit. No cylinder, no tank in the loft. They are compact and dominate smaller homes and flats, but they can struggle to feed multiple showers at once.

System and regular boilers heat radiators and a separate hot water cylinder, which stores hot water for the taps. Larger homes and homes with more bathrooms tend to have these.

Which type you have matters when you switch. A heat pump always heats water via a cylinder, so a home with a system boiler already has the plumbing logic in place. A combi home will need a cylinder added, which is a real cost and space line to plan for (covered in our boiler replacement guide).

One more piece of UK context: Northern Ireland is the exception to the gas-boiler story. Most NI homes heat with oil, and the grant landscape there is different too, as covered below. And whatever happens to your old boiler, disconnection and capping of gas pipework must be done by a Gas Safe registered engineer.

This comparison turned in the heat pump's favour as gas prices climbed, and the July 2026 cap change sharpens it. The Ofgem price cap rates (direct debit averages):

Ofgem price cap averages, accurate as at June 2026. The cap changes quarterly; your tariff may differ.

Here is the arithmetic that matters. Electricity costs roughly 3.6-4.3 times as much per kWh as gas, but a heat pump at SCOP 3.8-4.5 delivers 3.8-4.5kWh of heat per kWh of electricity. A boiler delivers slightly less than 1kWh of heat per kWh of gas. So on cap rates, a well-installed heat pump heats your home at or below gas-boiler cost, and the July 2026 gas rise (which pushes typical bills up around 13%) moves the line further in the heat pump's favour.

That is before tariffs. Several suppliers now offer time-of-use tariffs designed for heat pumps, with cheaper electricity in off-peak windows. Tariffs change too often to print rates here, but on the right one a heat pump runs meaningfully cheaper than gas rather than merely matching it. If you have solar panels, daytime running gets cheaper again.

Upfront cost is where the gas boiler has traditionally won, and where the grant changes the story. Indicative June 2026 figures:

• Air source heat pump: £8,000-14,000 installed before support, with the Ofgem-reported average around £12,500 for an 8kW system (January 2026). After the £7,500 Boiler Upgrade Scheme grant in England and Wales, most installations land at £500-6,500. Octopus reports averages around £4,460 after the grant, and many straightforward quotes come in near £1,000.
• Like-for-like boiler swap: usually cheaper upfront, but it recommits you to gas unit rates that just rose 27% in a quarter, plus a decade more of annual boiler servicing.

Two things push heat pump quotes toward the top of the range: converting a combi home (adding a hot water cylinder) and upgrading radiators so the system can run at efficient low flow temperatures. Both are one-off costs that a good MCS heat loss survey identifies before you commit.

Add the VAT advantage: residential heat pump installations carry 0% VAT until 31 March 2027 (5% after that), which is already reflected in quoted prices. The full grant detail, including the £9,000 uplift for oil and LPG heated homes from 21 July 2026, is in our Boiler Upgrade Scheme guide.

Where you live decides what help you get (accurate as at June 2026):

• England and Wales: the Boiler Upgrade Scheme pays £7,500 toward an air source or ground source heat pump, rising to £9,000 for homes heated by oil or LPG from 21 July 2026. The EPC certificate precondition was removed on 28 April 2026, and the scheme has been extended to 2030. Your MCS-certified installer applies and deducts the grant from the quote.
• Scotland: the Home Energy Scotland scheme offers a grant of up to £7,500 (up to £9,000 with the £1,500 rural and island uplift) plus an optional interest-free loan of up to £7,500 on top.
• Northern Ireland: no equivalent scheme exists. Limited energy-efficiency support is available; see niDirect for current schemes.
• UK-wide: 0% VAT on residential heat pump installations until 31 March 2027, automatic in the quote.

The full breakdown, including eligibility rules, is in our UK grants guide.

Air source heat pumps have no combustion: no flue, no burner, no carbon monoxide risk. Maintenance is light: keep the outdoor unit clear of leaves and debris, and have a periodic service per the manufacturer's schedule. With few wearing parts, well-installed units have long service lives.

Gas boilers need an annual service by a Gas Safe registered engineer to stay safe and keep their warranty valid, and carry the usual combustion wear items: ignition, fans, heat exchangers, valves.

Noise: a heat pump's outdoor unit produces a low fan hum. Modern units are quiet, but placement matters: keep it away from bedroom windows and neighbouring boundaries, and your installer will advise on siting rules for your property. A boiler is quiet but lives indoors, taking up cupboard space a heat pump frees up (though a cylinder claims some back).

Space: the heat pump needs an outdoor position with clear airflow, plus room for a hot water cylinder indoors if you do not already have one.

Trades: heat pump installation for the BUS grant must be carried out by an MCS-certified installer; decommissioning the old boiler and capping gas is work for a Gas Safe registered engineer.

For most UK households whose boiler is approaching end of life, the heat pump is now the better long-term choice. How to think about it:

Strong candidates for an air source heat pump:

• Anyone whose gas boiler is 10+ years old and due for replacement anyway: the £7,500 grant closes most of the price gap
• Oil and LPG heated homes, who get the £9,000 BUS uplift from 21 July 2026 and currently pay for delivered fuel
• Households with solar panels or willing to use heat pump time-of-use tariffs
• Homes with decent insulation, or owners happy to improve it as part of the project
• Anyone who wants off gas before further unit-rate rises: the cap rose 27% on gas in a single quarter in July 2026

Situations where a boiler may still make sense for now:

• A recent, working boiler: run it toward end of life rather than scrapping it early, and plan the switch for when it fails
• Homes with no workable outdoor location for the unit or indoor space for a cylinder
• Northern Ireland households for whom no grant support exists; the maths still works for some, but without £7,500 of help

If your boiler is ageing, the smart move is to decide your replacement before it dies, not the freezing morning it does. Get free quotes from local installers to see real numbers for your home.