Air Source vs Ground Source Heat Pumps: Which Is Best?

Choosing between air source and ground source heat pumps is one of the biggest decisions you'll make when switching to renewable heating. Both types work on the same principle—extracting heat from the environment—but they differ significantly in cost, installation, and suitability.

Head-to-Head Comparison

Factor	Air Source (ASHP)	Ground Source (GSHP)
Installed Cost	£7,000 - £15,000	£15,000 - £35,000
After BUS Grant	£0 - £7,500	£7,500 - £27,500
Efficiency (COP)	2.5 - 4.0	3.5 - 5.0
Installation Time	2-4 days	1-2 weeks
Garden Space Needed	~1m² (outdoor unit)	200-400m² or borehole access
Noise Level	40-50 dB (outdoor unit)	Silent (underground)
Lifespan	15-20 years	20-25 years (ground loops 50+ years)
Maintenance	Annual service £100-200	Annual service £100-200
Planning Permission	Usually not required	Sometimes required

Air Source Heat Pumps (ASHP)

Air source heat pumps extract heat from the outside air, even when temperatures drop to -15°C. They're the most popular choice in the UK, accounting for over 90% of installations.

Pros:

Much lower upfront cost (£7,000-£15,000)
Quick and easy installation (2-4 days)
Minimal garden disruption
Suitable for most properties
Well-proven technology with many installer options

Cons:

Slightly lower efficiency than ground source
Outdoor unit produces some noise (similar to air conditioning)
Efficiency drops in very cold weather (though still works)

Ground Source Heat Pumps (GSHP)

Ground source heat pumps extract heat from the ground via buried pipes (horizontal loops) or deep boreholes. The ground maintains a constant 10-12°C year-round, providing consistent efficiency.

Pros:

Higher efficiency (15-20% better than air source)
Consistent performance regardless of air temperature
Silent operation (no outdoor unit)
Longer lifespan (ground loops last 50+ years)
Can provide cooling in summer

Cons:

Much higher cost (£15,000-£35,000)
Requires significant garden space or borehole drilling
Major installation disruption to garden
Fewer qualified installers
May need planning permission

Which Should You Choose?

Choose an air source heat pump if:

You have a typical UK home (flat, terrace, semi, or standard detached)
Budget is a consideration
You don't have a large garden
You want a straightforward installation
You need it installed quickly

Consider a ground source heat pump if:

You have a large property with significant land
Budget isn't a major constraint (£20,000+ available)
You're building a new home (installation is easier)
Noise from an outdoor unit is a concern
Maximum efficiency is a priority
You want to add cooling capability

Running Cost Comparison

For a typical 3-bedroom semi-detached home:

System	Annual Running Cost	15-Year Running Costs
Air Source Heat Pump	£750/year	£11,250
Ground Source Heat Pump	£620/year	£9,300
Difference	£130/year	£1,950

The ground source saves about £130/year in running costs. But with an extra £10,000-£15,000 upfront cost, it would take 77-115 years to pay back the difference—far longer than the system's lifespan.

Frequently Asked Questions

Which is better: air source or ground source heat pump?

For most UK homes, air source heat pumps are the better choice due to lower cost (£7,000-£15,000 vs £15,000-£35,000), easier installation, and similar efficiency in UK climates. Ground source is better for larger properties with land and bigger budgets.

Are ground source heat pumps more efficient?

Yes, ground source heat pumps are typically 15-20% more efficient because ground temperatures are constant year-round. However, the higher efficiency rarely justifies the extra £10,000-£20,000 cost for average homes.

How much space do I need for a ground source heat pump?

Horizontal ground loops need approximately 2-3 times your home's floor area. Vertical boreholes need less space but cost more. Air source heat pumps only need about 1m² outside space.