Hybrid heat pump vs air source heat pump

How each system works

An air source heat pump on its own replaces the boiler. It heats the radiators or underfloor heating and, with a cylinder, the hot water. The gas boiler is removed, and if nothing else in the home uses gas, the gas supply can be capped.

A hybrid keeps a boiler, usually gas, connected to the same heating system as a heat pump. The controls decide which one runs: typically the heat pump covers mild weather and much of the year, and the boiler covers the coldest days, the hot water, or both. Some hybrids are designed as a single package; others are a heat pump added to an existing boiler.

The grant: the deciding difference

GOV.UK states it plainly: you cannot get a Boiler Upgrade Scheme grant for a hybrid heat pump system, and it gives a gas boiler with an air source heat pump as the example. The scheme exists to replace fossil fuel heating, so any job that leaves a working boiler connected falls outside it. The full exclusions list, from hybrids to social housing, is on hybrid heat pump grant and other exclusions.

A full air source system, by contrast, gets £7,500 off the price in England and Wales, or £9,000 where the home has no mains gas connection and the system being replaced runs on oil or LPG, for applications up to 31 March 2027. For most homeowners that single rule settles the comparison, because it is worth thousands of pounds on day one.

Running costs at the cap

The assumption behind most hybrids is that gas is cheaper in winter. At the Ofgem cap for 1 October to 31 December 2026, gas is 7.97p per kWh and electricity 26.32p. Heat from a 90% efficient gas boiler costs about 8.9p per kWh; heat from a heat pump at a seasonal efficiency of 3 costs about 8.8p. The two are within 0.1p of each other, so on these prices there is little saving from switching to gas for part of the year.

Two things tip it further. A hybrid keeps a gas supply, and with it the gas standing charge of about £108 a year at the cap, which a heat pump-only home can drop. And a heat pump runs less efficiently on the coldest days: in the Electrification of Heat trial the median air source system’s efficiency was 2.37 at minus 3°C, against a peak of 3.37 at 10°C. That is the case for a hybrid in a very cold week, and it is real, but it applies to a small share of the year. The running costs comparison shows the full sum.

Upfront cost

There is no official installed-cost figure for hybrids, so we do not give one. What can be compared is the grant. The DESNZ median for a grant-funded air source heat pump was £12,826 in 2026 Q3, including the grant value, which leaves about £5,326 after the £7,500 grant. A hybrid quote carries no grant at all. A hybrid may need less work in some homes, for example fewer radiator changes, because the boiler covers the peaks; ask any installer quoting a hybrid to price the full heat pump system for the same house too, so you can see the difference with the grant taken off.

When a hybrid makes sense

• The boiler is new. If you fitted a boiler recently and want to add a heat pump without scrapping it, a hybrid uses what you have, at the cost of the grant.
• The house cannot be adapted yet. If radiators or pipework cannot be changed for now, a hybrid can run the heat pump at low temperature most of the year and leave the peaks to the boiler.
• You are not eligible for the grant anyway. In Scotland or Northern Ireland, or in social housing, the Boiler Upgrade Scheme does not apply, so the grant gap does not exist.

For most owner-occupied homes in England and Wales replacing a boiler, the grant and the close running costs point to a full heat pump. The Electrification of Heat project found no property type or era unsuitable for one; see which homes are not suitable for a heat pump.

Side by side