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Air Source vs Ground Source Heat Pump — UK
Comparing ASHP and GSHP for UK homes — COP ratings, installation costs, space requirements, running costs and BUS grant eligibility.
Side-by-Side Comparison
| Property | Air Source (ASHP) | Ground Source (GSHP) |
|---|---|---|
| COP (seasonal average) | 2.8-3.5 | 3.5-4.5 |
| Installation cost | £8,000-14,000 | £15,000-25,000 |
| BUS grant (2026) | £7,500 | £7,500 |
| Net cost after grant | £500-6,500 | £7,500-17,500 |
| Running cost (3-bed semi) | £700-1,000/year | £500-800/year |
| Space required | ~1m x 1m outdoor unit | 200m² garden or borehole |
| Installation time | 2-3 days | 3-5 days (trenches) or 1-2 weeks (borehole) |
| Disruption | Minimal | Significant (garden excavation) |
| Noise | 40-55 dB at 1m | Silent externally |
| Lifespan | 15-20 years | 20-25 years (ground loop: 50+) |
Pros and Cons
Air Source Heat Pump
Pros
- + Much cheaper to install
- + No garden excavation needed
- + Quick installation (2-3 days)
- + Suits any property with outdoor space
- + Eligible for £7,500 BUS grant
Cons
- - Lower efficiency in cold weather
- - Outdoor unit produces noise
- - Performance drops below 0°C
- - Higher running costs than GSHP
- - Defrost cycles use energy
Ground Source Heat Pump
Pros
- + Highest efficiency (COP 3.5-4.5)
- + Consistent performance year-round
- + Silent operation (no outdoor unit)
- + Lower running costs
- + Ground loop lasts 50+ years
Cons
- - Much higher installation cost
- - Needs large garden or borehole
- - Significant installation disruption
- - Longer installation time
- - Longer payback period vs ASHP
UK Cost Comparison (2026 Prices)
For a typical 3-bedroom semi-detached house (10kW heat demand):
| Cost Element | ASHP | GSHP (borehole) |
|---|---|---|
| Heat pump unit | £3,500-5,500 | £5,000-8,000 |
| Ground loop / borehole | N/A | £5,000-10,000 |
| Hot water cylinder | £800-1,500 | £800-1,500 |
| Pipework, controls, commissioning | £2,500-4,000 | £3,000-4,500 |
| Total before grant | £8,000-12,000 | £15,000-24,000 |
| BUS grant | -£7,500 | -£7,500 |
| Net cost | £500-4,500 | £7,500-16,500 |
| Annual running cost | £700-1,000 | £500-800 |
When to Choose Each
Choose Air Source When
- Budget is limited
- Small or no garden
- Quick installation needed
- Retrofitting to existing property
- Most UK domestic situations
Choose Ground Source When
- Large garden available
- Maximum efficiency is the goal
- Noise is a concern (neighbours)
- New build (install during groundworks)
- Long-term investment property
Related Calculators
- Heat Pump Sizing Calculator — calculate the right heat pump output for your property
Next up: related pages
How We Calculate This
Frequently Asked Questions
Ground source heat pumps have a higher COP (Coefficient of Performance) — typically 3.5-4.5 vs 2.8-3.5 for air source. This is because ground temperature is a stable 8-12°C year-round, while air temperature drops to 0-5°C when you need the most heat. Ground source delivers 20-30% more heat per unit of electricity.
Air source: £8,000-14,000 installed (before grant). Ground source: £15,000-25,000 installed (borehole) or £12,000-20,000 (horizontal trenches). The Boiler Upgrade Scheme (BUS) grant gives £7,500 towards either type, bringing ASHP to £500-6,500 and GSHP to £7,500-17,500 net cost.
For horizontal ground loops, you need roughly 2-3 times your property floor area in garden space (e.g., 200m² for a 3-bed house). Vertical boreholes need minimal space (2m x 2m per borehole) but cost more to drill. Air source heat pumps just need an outdoor wall or flat area (about 1m x 1m) with good airflow.
Air source heat pumps produce 40-55 dB at 1 metre — similar to a fridge or quiet conversation. Planning guidance requires them to be below 42 dB at the nearest neighbour boundary. Ground source heat pumps are virtually silent externally as the compressor is usually indoors. Noise is primarily a factor with ASHP.
Yes. The Boiler Upgrade Scheme (BUS) provides £7,500 towards both air source and ground source heat pumps. The property must have an EPC (or be listed/exempt), and the installer must be MCS-certified. The heat pump must replace an existing fossil fuel heating system. The grant is available in England and Wales until 2030.
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Last updated: April 2026
Verified against UK standards · estimates only, confirm with your supplier.