Air-to-air vs air-to-water: why the grants are different
Grant values for the two heat-pump types
The Boiler Upgrade Scheme pays £2,500 towards an air-to-air heat pump in a residential property. Air-to-water and ground-source heat pumps normally receive £7,500. Both are government grants under the same scheme; the amount depends on the system installed and the property's circumstances.
From 21 July 2026 until 31 March 2027, an eligible off-gas-grid property replacing oil or LPG heating can receive £9,000 towards an air-to-water or ground-source heat pump. That temporary uplift does not apply to air-to-air heat pumps, so £2,500 is the figure for an eligible air-to-air installation.
See which grant applies to your home — five questions.
Check eligibilityWhat each system actually does
An air-to-air heat pump is the wall-mounted unit most people call air conditioning. It moves heat between the outside air and the air in your rooms — cooling in summer, heating in winter. Most systems deliver heat to rooms rather than water; an installer must confirm any domestic-hot-water provision in the proposed design.
An air-to-water heat pump heats water in a cylinder, which then feeds your radiators (or underfloor heating) and your hot taps. It replaces a gas boiler like-for-like on the water side. Ground-source systems do the same, but draw heat from pipes buried in the garden.
Why the grant differs
The government sets the air-to-air grant at £2,500 for residential properties. Air-to-water and ground-source grants are normally £7,500, rising to £9,000 from 21 July 2026 until 31 March 2027 for eligible off-gas-grid oil or LPG replacements. Installation scope and cost vary by property and installer.
An air-to-air system uses an outdoor unit, indoor head and refrigerant line. The installer must set out how the proposed system will meet the property's hot-water needs and whether any supplementary appliance is required; see our guide on hot water for the questions to ask.
Which one fits your home
If you want cooling in summer as well as heating, or you live in a flat where running new pipework is impractical, air-to-air is usually the right answer. If you already have wet central heating and want to replace the boiler directly, air-to-water is normally the better match.
An MCS-certified installer will assess your home and quote for the system that suits it, applying for the correct grant on your behalf.