Air source vs ground source heat pump: which suits a commercial building?
This air source vs ground source heat pump guide sets out where each type wins for a commercial building, what it costs to compare them, and how to decide.
Air source vs ground source heat pump: the short answer
In the air source vs ground source heat pump decision, both types move heat from a source into your building using a refrigerant cycle. An air source heat pump takes heat from outdoor air through a fan-driven coil. A ground source heat pump takes heat from the ground, or from groundwater, through a buried loop, boreholes or an open-loop water supply. The ground stays steadier in temperature than winter air, which is the physical reason ground source tends to reach a higher seasonal efficiency.
That efficiency advantage is bought with ground works. For most commercial buildings the real question is not which type is better in the abstract, but whether your site has the land, the ground and the budget to make the ground-source advantage worth having. Air source wins on simplicity and cost; ground source wins where the ground can be used and the heat load is large, steady or both heating and cooling. The sections below take each factor in turn.
Side-by-side comparison
The table is directional. It describes how the two types usually compare, not a promise for any particular site. Where a figure is shown it comes from one published installer guide (a secondary source) or from the scheme rules; test every line against your own survey.
| Factor | Air source | Ground source |
|---|---|---|
| Efficiency (SCOP direction) | Lower in cold weather because the outdoor coil works against cold air and needs defrost cycles. | Usually higher and steadier, because the ground temperature changes little through the year. See the SCOP explainer. |
| Capital cost direction | Lower. Planning bands: £55,000–95,000 at 100 kWth; £80,000–250,000 at 200–500 kWth; £210,000–380,000 at 500 kWth. | Higher. Planning bands: £90,000–160,000 at 100 kWth; £120,000–600,000 at 200–500 kWth; £360,000–640,000 at 500 kWth. |
| Land and boreholes | Needs outdoor space or roof for units and clearance for airflow; no ground works. | Needs a trench field, boreholes or an open-loop water source, with access for drilling or digging. |
| Planning | Commercial premises: check your local planning authority. A noise assessment to BS 4142 is commonly requested. | Mostly below ground, but drilling compounds, manifolds and any abstraction need consideration. Check the planning authority. |
| Noise | Fans and compressors are outdoors, so siting and neighbours matter. | Plant sits indoors with the ground loop silent; no outdoor fan noise, though a plant-room noise check is still worthwhile. |
| Space | Outdoor footprint for each unit or cascade, plus service access. | Plant room space plus the ground-loop area, which can be large. |
| Maintenance | Outdoor coils, fans and defrost components need attention; units are exposed to weather. | Outdoor coils and fans are exposed to weather and need inspection; a buried loop has no outdoor fans, but pumps and controls still need servicing. |
| BUS funding | Eligible within the size limits (£7,500 grant); not for hybrids. | Eligible within the size limits (£7,500 grant); a shared ground loop is allowed up to 300 kWth in total. |
| Running-cost direction | Higher energy use per unit of heat than ground source, all else equal. | Lower energy use per unit of heat, which can offset the higher capital cost over time. |
The cost bands overlap and are not consistent with each other; they are one published guide’s planning ranges, not a quote and not a typical price. The cost guide explains how to compare quotes properly.
When an air source heat pump wins
Air source is usually the practical choice when one or more of these apply:
- No usable land. Town-centre sites, multi-tenant buildings and sites with buried services across the plot rarely have room for a ground loop or a drilling rig.
- Tight budget or short horizon. Lower capital cost matters most when you lease the premises or cannot commit capital for a long payback.
- Roof or yard space exists. Units can sit on a flat roof, in a yard or beside the plant room, and can be added in modules as the load grows.
- Retrofit with disruption limits. No drilling, no excavation and no ground reinstatement.
- Partial or phased replacement. A cascade of modular units or a hybrid layout can keep the existing boiler for peak days; see the commercial air source heat pump guide and the hybrid retrofit page.
The trade-offs are cold-weather efficiency, defrost, and outdoor noise. If the nearest neighbour is close, that third item can decide the whole project.
When a ground source heat pump wins
Ground source earns its extra cost where the ground can be used and the building asks a lot of it:
- Land is available. A car park, field or green space can take a horizontal trench field or a borehole array, subject to the ground study.
- Boreholes are practical. Where there is a drilling route and a small compound area, vertical boreholes need very little surface area for their capacity.
- Simultaneous heating and cooling. A building that needs both at once, for example a data room beside office space, can use a shared loop and pass heat between zones. The ambient loops and heat networks guide covers shared-loop designs.
- Large, steady loads. Longer running hours spread the capital cost over more delivered heat, so the efficiency gain is worth more.
- New build. Ground works can be planned with the site works, low-temperature emitters are easier to specify, and the loop does not need retrofitting around existing services.
For fuller design detail, see the commercial ground source heat pump guide. The planning bands above show the cost penalty is real, so ground source works best when the efficiency gain, the funding and the site conditions all line up.
Funding under the Boiler Upgrade Scheme
The Boiler Upgrade Scheme (BUS) covers air-to-water and ground-source heat pumps in England and Wales, including a building used for your business. It does not cover buildings that need a larger system than its limits allow, and the sizes matter:
- Single heat pump: up to 45 kWth.
- Multi-heat-pump (cascade) system serving one property under one voucher: up to 70 kWth.
- Shared ground loop: up to 300 kWth in total, with each heat pump no more than 45 kWth.
The grant is £7,500 for an air-to-water or ground source heat pump, or £9,000 where the property is off the gas grid and replaces oil or LPG (21 July 2026 to 31 March 2027). You must own the property, the system being replaced must be fossil-fuel or direct electric, and the application is made by the MCS-certified installer on your behalf; the grant is taken off the quote. A hybrid system (a heat pump kept alongside a gas boiler) is not eligible, and a heat pump that has received any other public grant is not eligible either.
Most medium and large commercial plant exceeds these limits, in which case BUS does nothing for that building. The business premises BUS guide sets out the rules and the funding overview covers what has closed. Funding does not favour one type over the other in the amount, but the shared-ground-loop allowance makes ground source workable for a cluster of smaller units on one site.
Running cost: do not assume ground source is cheaper to run
Ground source normally delivers more heat per unit of electricity, but that only helps you if the arithmetic works against your current fuel. Cost per kWh of heat equals the unit price divided by the efficiency, and the break-even SCOP against gas rises as electricity gets dearer relative to gas. The running costs versus gas guide works through this, and the savings calculator lets you use your own tariffs.
DESNZ Quarterly Energy Prices for Q1 2026 (provisional, excluding VAT, including Climate Change Levy) give medium-sized businesses 25.0p per kWh for electricity and 4.55p per kWh for gas. At an assumed 88% boiler efficiency, gas heat costs about 5.17p per kWh of heat. A heat pump needs a SCOP above about 4.8 (25.0 ÷ 5.17) to match gas on energy cost alone at those prices. Whether either type reaches that depends on flow temperature, controls and your actual tariff, so treat the number as a test to apply to quotes rather than a forecast.
In short, ground source widens the margin but does not guarantee a saving. Capital cost, funding, maintenance, tariff and any cooling benefit all enter the comparison.
Ground investigation: what has to happen first
An air source system can be sized from heat-loss data and a site visit. A ground source system cannot be priced firmly until the ground has been looked at. Typical steps are:
- Desk study. Geology, groundwater, nearby boreholes, buried services, contaminated land and any protected areas.
- Test borehole and thermal response test. A test borehole is drilled and heated or cooled for a period while temperatures are logged. The result gives the ground’s effective thermal conductivity, which sets how many boreholes (or how much trench length) the load needs.
- Design of the loop field. Spacing, depth and fluid are set against annual heat extraction and heat rejection, so the ground does not slowly cool or warm over the years.
- Drilling and installation. Boreholes need a drilling rig, access, spoil handling and reinstatement. Horizontal trenches need excavation across the field area.
- Open-loop systems. Taking water from an aquifer or river and returning it is subject to abstraction and discharge rules. Check Environment Agency requirements, and the Scottish, Welsh or Northern Irish regulator where relevant, before committing to an open-loop design.
Ask for the thermal response test result and the borehole count in any ground-source quote. If a quote has neither, the price is an estimate against unknown ground. The sizing guide shows how the building’s load feeds the design.
A decision checklist
Work through the list in order; stop at the first answer that rules a type out.
- What is the design heat load, and is it within the BUS limits (45, 70 or 300 kWth) if you intend to claim?
- Is there land, a car park or a drilling route? If not, ground source is probably out.
- Who owns the property? BUS needs the owner as applicant.
- Where would air source units sit, and how close are neighbours? Plan for a BS 4142 noise assessment.
- Do you need cooling as well as heating, and at the same time? That favours a shared loop.
- What flow temperature do your emitters need? Lower flow temperatures favour either type; high flow temperature favours neither.
- Can the electricity supply take the load? Ask your DNO early about capacity.
- What is the capital budget, and how long will you hold the building? A short horizon points to air source.
- Get at least two quotes for each type that you consider viable, with the same specification and metering, then compare.
If you want comparable quotes, you can send your details through the quote form; check any installer’s MCS and other credentials on the public registers before you sign.