Home energy guide
Air source vs ground source heat pumps: which suits your home?
For most homes, air source is the sensible pick: cheaper and easier to fit. Ground source costs more and needs land or a borehole, but it stays more efficient in the depths of winter. Here's how to choose.
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The quick comparison
Air source costs about £12,000 fitted; ground source about £15,000 with trenches, and a lot more with a borehole. Both get the same £7,500 grant. Ground source is quieter outside and often more efficient, but it needs a big garden or a drilling rig.
See the numbers
| Air source | Ground source | |
|---|---|---|
| Typical installed cost | About £12,000 | About £15,000 with trenches; considerably more with a borehole |
| Boiler Upgrade Scheme | £7,500 | £7,500 |
| Cost after grant | About £4,500 | About £7,500+ |
| Outdoor space | Wall or ground space for a fan unit | Garden for trenches, or room for a drilling rig |
| Indoor space | Hot-water cylinder (cupboard about 80 × 80 cm) | Indoor unit about the size of an American fridge (120 × 60 × 60 cm) |
| Noise outside | Fan unit makes some noise | Nothing outside once buried |
VAT: installations in homes are zero-rated until 31 March 2027, then 5% (HMRC). At 5%, the same £12,000 and £15,000 jobs would be £12,600 and £15,750.
Air source: the popular choice
A fan unit outside pulls heat from the air, even on cold days. The Energy Saving Trust describes two types:
- Monobloc: everything in one outdoor box, with water pipes into the house. Cheaper and quicker to fit, slightly less efficient.
- Split: an indoor and an outdoor unit. Can be more efficient, but costs more.
The unit needs breathing space around it. Its one weakness: it gets less efficient as the air gets colder, which is exactly when you want the most heat.
Ground source: the steady performer
Buried pipes carry a water-and-antifreeze mix that collects heat from the ground. The ground stays a steadier temperature than the air all winter, which helps efficiency. There are two ways to bury the pipe:
- Trenches. For a new-build three-bed, EST suggests two trenches of 30–40 metres. Older or bigger homes need more. The ground must be diggable, tree-free and reachable by machinery.
- Boreholes. Narrow (about 20 cm) but deep: 75–200 metres, depending on your heat needs and the geology. Pricier, usually needs a ground survey, but can be more efficient because deeper ground is warmer. Bigger homes may need more than one.
The digging and drilling also gets 0% VAT until 31 March 2027 (HMRC).
Running costs
The more efficient the heat pump (its SCOP), the cheaper each unit of heat. At today's cap, heat costs about 9.4p a unit at SCOP 2.8, but only 6.6p at SCOP 4.0.
Ground source often reaches a higher SCOP, but it depends heavily on the design. We couldn't find an official figure for the typical gap that we could verify today, so we don't quote one. Ask each installer for the predicted SCOP at your design flow temperature; MCS installers should provide it.
See the numbers
Cost per unit of heat = electricity price ÷ SCOP, at the October–December 2026 cap of 26.32p:
- SCOP 2.8: 9.4p per kWh of heat
- SCOP 3.5: 7.5p per kWh of heat
- SCOP 4.0: 6.6p per kWh of heat
A worked example
Picture a home needing 12,000 kWh of heat a year. A ground source system might save about £222 a year over air source. If it costs £3,000 more after the grant, the extra pays back in roughly 13.5 years.
See the numbers
- Air source at SCOP 3.0: 4,000 kWh of electricity, about £1,053 a year at 26.32p.
- Ground source at SCOP 3.8: 3,158 kWh, about £831 a year.
- These SCOPs are illustrations. Use your installers' figures in the heat pump calculator.
When ground source is worth a look
- a big garden or paddock with easy machine access;
- a large or older home that needs lots of heat, so the efficiency gain is worth more;
- worries about noise or space for an outdoor fan unit;
- a renovation or new driveway where the ground is being dug up anyway;
- shared ground loops for terraces or flats, which spread the cost.
When air source is the better bet
- a small garden, or none;
- a well-insulated home that doesn't need much heat;
- a tighter budget.
Flats and homes without outdoor space
Compact heat pumps can suit small, well-insulated flats, needing a cupboard of about 80 × 80 cm near an outside wall (EST). Air-to-air heat pumps are another option, with a smaller £2,500 grant. In Guernsey and Jersey, check the rules for outdoor units in our planning guide.
Frequently asked questions
Is ground source more efficient than air source?
Usually, because the ground stays warmer than winter air. How much depends on the design and flow temperature, so ask installers for the predicted SCOP.
How much land do I need for a ground source heat pump?
The Energy Saving Trust suggests two trenches of 30–40 metres for a new-build three-bedroom house. If space is short, a borehole of 75–200 metres deep may work instead.
Do both get the same grant?
Yes. The Boiler Upgrade Scheme gives £7,500 for air or ground source in England and Wales.
Can I have a heat pump in a flat?
Sometimes. Compact heat pumps can suit small, well-insulated flats, and air-to-air units are another option.
Related guides
- Heat pump vs gas or oil boiler: running costs
- The Boiler Upgrade Scheme: who gets the £7,500 heat pump grant
- Electricity tariffs for heat pumps: how time-of-use cuts running costs
- Do you need planning permission for a heat pump?
- Heat pump sizing, flow temperatures and radiators
- All home-energy calculators
Sources (checked 27 October 2026 unless stated)
- Energy Saving Trust: Air source heat pumps: £12,000, monobloc and split, cylinder space, flats
- Energy Saving Trust: Ground source heat pumps: about £15,000 with trenches, trench and borehole sizes, indoor unit size
- GOV.UK: Boiler Upgrade Scheme: £7,500 and £2,500
- HMRC VAT Notice 708/6: energy-saving materials: heat pumps and groundworks zero-rated to 31 Mar 2027
- Ofgem: price cap 1 Oct–31 Dec 2026 (published 26 Aug 2026): 26.32p/kWh
- Typical SCOP gap between air and ground source: not verified; example SCOPs are our assumptions