Guide · Updated 8 November 2026
Air source vs ground source heat pumps
Ground source heat pumps draw heat from pipes buried in the garden or a borehole, so they're very efficient but cost far more to install and need land. Air source heat pumps take heat from the outside air and are cheaper and easier to fit. Air to air is the simplest and cheapest kind of air source heat pump, and the only one that also cools.
Three types compared
| Air to air | Air to water | Ground source | |
|---|---|---|---|
| Heat source | Outside air | Outside air | Ground (trench or borehole) |
| Delivers heat by | Warm air from wall or ducted units | Radiators or underfloor | Radiators or underfloor |
| Hot water | No | Yes | Yes |
| Cooling | Yes | Rarely | Rarely |
| Grant (England and Wales) | £2,500 | £7,500 | £7,500 |
| Garden needed | No | Space for the outdoor unit | Yes, or a borehole |
| Relative install cost | Lowest | Middle | Highest |
Efficiency
The ground stays at a fairly steady temperature all year, so ground source systems keep their efficiency on cold days better than air source. Air source systems, including air to air, lose some efficiency in freezing weather but have improved a lot, and their much lower installation cost often outweighs the difference.
Which to choose
- Flat or small home, no radiators, wants cooling: air to air.
- House with radiators and a standard garden: air to water.
- Rural house with land, high heat demand, long-term owner: ground source is worth pricing.
Questions
Is ground source better than air source?
It's usually more efficient, especially in cold weather, but costs much more to install and needs land or a borehole. For most homes air source gives better value.
Is an air to air heat pump an air source heat pump?
Yes. It's a type of air source heat pump that delivers heat as warm air rather than hot water.
Sources
Checked 8 November 2026.