At-a-Glance Comparison
| Feature | Air Source (ASHP) | Ground Source (GSHP) | Hybrid |
|---|---|---|---|
| Cost (before grant) | £7,000-£13,000 | £15,000-£35,000 | £5,000-£10,000 |
| Cost (after £7,500 BUS) | £0-£5,500 | £7,500-£27,500 | Not eligible |
| Efficiency (COP) | 3.0-3.8 | 3.8-4.5 | 2.5-3.5 (heat pump mode) |
| Space required | Outdoor wall space | Large garden / borehole | Outdoor wall space |
| Noise level | 40-50 dB | Virtually silent | 40-50 dB |
| Lifespan | 15-20 years | 20-25 years | 15 years |
| Best for | Most UK homes | Large rural properties | Older homes, transition |
| Installation time | 2-3 days | 2-4 weeks | 1-2 days |
| Planning permission | Usually not needed | May be needed | Usually not needed |
Air Source Heat Pumps (ASHP)
Advantages
- • Most affordable heat pump type
- • £7,500 BUS grant eligible
- • Suitable for most UK homes
- • Quick installation (2-3 days)
- • No garden excavation needed
- • Permitted development (usually)
Considerations
- • Efficiency drops in very cold weather
- • External unit produces some noise
- • Lower COP than ground source
- • Needs adequate outdoor space
- • May need radiator upgrades
Air source heat pumps are by far the most popular choice, accounting for over 85% of UK heat pump installations. They work by extracting heat from outside air - even at temperatures as low as -15°C - and concentrating it to heat your home and hot water. Modern ASHPs achieve a Coefficient of Performance (COP) of 3.0-3.8, meaning for every 1kW of electricity consumed, they produce 3-3.8kW of heat.
Ground Source Heat Pumps (GSHP)
Advantages
- • Highest efficiency (COP 3.8-4.5)
- • Consistent performance year-round
- • Virtually silent operation
- • Longest lifespan (20-25 years)
- • No visible external unit
- • £7,500 BUS grant eligible
Considerations
- • Significantly higher upfront cost
- • Requires garden or land for ground loops
- • Major installation disruption (2-4 weeks)
- • Borehole drilling is expensive
- • May need planning permission
Ground source heat pumps extract heat from underground via a network of buried pipes filled with a water-antifreeze mixture. Because ground temperatures in the UK remain a consistent 8-13°C year-round, GSHPs maintain higher efficiency than ASHPs, especially in winter. They're ideal for larger, rural properties with available land.
Hybrid Heat Pumps
A hybrid system combines a small air source heat pump with your existing gas or oil boiler. The heat pump handles mild-weather heating (typically 80% of the year), while the boiler kicks in during the coldest spells. This is a good transitional option for older, poorly-insulated homes where a full heat pump may not yet be practical.
Note: Hybrid heat pumps are not eligible for the £7,500 BUS grant. They're best viewed as a stepping stone before committing to a full heat pump when you improve your home's insulation.