Guide · Updated 8 November 2026
Air to air vs air to water heat pumps
An air to water heat pump heats water for radiators or underfloor heating and your hot water; an air to air heat pump blows warm (or cool) air into rooms and doesn't heat water. Air to air is much cheaper and quicker to install and suits flats and smaller homes without radiators. Air to water suits houses with a wet heating system and gets a larger grant (£7,500 against £2,500).
Compared
| Air to air | Air to water | |
|---|---|---|
| Heats | Air in each room | Water for radiators or underfloor |
| Hot water | No (needs a separate solution) | Yes, with a cylinder |
| Cooling | Yes | Rarely in UK homes |
| Typical installed cost | About £4,500 for a flat or small house | Typically £8,000 to £16,500 |
| Boiler Upgrade Scheme grant | £2,500 | £7,500 |
| Install time | 1 to 3 days | Often 3 to 5 days, more with radiator changes |
| Space needed indoors | Wall units only | Hot water cylinder, sometimes a buffer tank |
Air to air suits
- flats and small homes, especially those on electric heating with no radiators
- homes with no room for a hot water cylinder
- people who want cooling in summer
- loft conversions, extensions and garden rooms
Air to water suits
- houses that already have radiators and a gas or oil boiler
- larger homes where one outdoor unit can heat everything through the existing pipes
- households that want the heat pump to do the hot water too
- people who'd rather not have wall units in every room
Comfort and feel
Air to air heats quickly: rooms warm up in minutes. Some people notice the air movement, especially on a high fan speed. Air to water gives the gentler, steady radiant heat of radiators but takes longer to warm a cold house.
Can you have both?
Yes, but you can only claim one Boiler Upgrade Scheme grant per property.
Questions
Which is better, air to air or air to water?
Neither is better for every home. Air to air is cheaper and suits flats and homes without radiators, and it can cool. Air to water suits houses with radiators and heats your hot water too.
Does an air to air heat pump heat water?
No. You'll need a separate way to heat water, such as an electric cylinder or a hot water heat pump. A few products, such as Daikin Multi+, combine both.
Why is the grant smaller for air to air?
Air to air systems are much cheaper to install. £2,500 covers more than half of a typical £4,500 install, which is a similar share to the £7,500 grant on an air-to-water system.
Sources
- GOV.UK: Discounts for families to keep warm in winter and cool in summer (18 Nov 2025)
- GOV.UK: Boiler Upgrade Scheme, what you can get
- ExpertSure: Air-to-air heat pumps (cost ranges, Oct 2026)
- Daikin: Your guide to the latest BUS changes
Checked 8 November 2026.