Warmer homes, off fossil fuels

How a heat pump works

A heat pump does not burn anything. It works like a fridge in reverse: it uses a small amount of electricity to gather warmth from the outside air (even on a cold day there is plenty of heat in the air) and concentrate it to heat your home and hot water. An air source heat pump sits outside like an air-conditioning unit; a ground source heat pump draws warmth from pipes buried in the ground.

Why it works, even here, even in winter

Because it moves heat rather than making it, a heat pump delivers roughly three to four units of heat for every one unit of electricity. That ratio is its Seasonal Coefficient of Performance (SCOP), and across hundreds of monitored UK homes it averages around three. A gas boiler, by contrast, always gives less than one unit of heat per unit of fuel.

Heat pumps run at a lower temperature over longer periods than a boiler, keeping your home steadily and evenly warm rather than blasting hot then cooling. They work in a Sussex winter when the system is designed properly. Read our winter explainer.

What to look for (this is where it is won or lost)

• A proper heat loss survey. Insist on a room-by-room calculation of your home's heat loss, not a quick estimate. This sizes the system correctly, which is the single biggest factor in comfort and running cost.
• The right radiators. Because the water runs cooler, some radiators may need to be a size larger, or underfloor heating used. A good installer will tell you which.
• A low flow temperature. A well-designed system runs at a low flow temperature (ideally around 35 to 45°C), which is what keeps it efficient and cheap.
• An MCS-certified installer. Required to access the grant and to do the job to standard. Check them on the MCS register and see our vetted list.
• Fabric first. A bit of insulation and draught-proofing first can mean a smaller, cheaper heat pump and lower bills. See our home energy checklist.

The cost, and the grant

The Boiler Upgrade Scheme currently takes up to 9,000 pounds off an air source heat pump fitted by an MCS installer, paid straight to the installer so it comes off your quote. What you pay after that depends on your home and the radiators needed. We will review any quote free of charge. More detail on our grants page.

Biomass and other options

For some rural, off-gas homes a biomass (wood pellet or log) boiler can suit, especially larger or harder-to-heat properties. Read our biomass guide.

Go deeper

Our full, plain-English guides: Air source heat pumps explained, Do heat pumps work in winter?, and Biomass heating.