Ground source heat pump borehole cost: what drives it on a commercial site

Why borehole cost is hard to quote from a desk

Searches for ground source heat pump borehole cost are mostly answered with householder figures: one or two holes behind a house. A commercial borefield is a different job. It may be tens of boreholes, laid out in a grid on a car park or playing field, sized to a heat load that a gas bill and a heat-loss calculation have to establish first. The cost does not scale in a straight line with kW, because the amount of drilling needed depends on what the ground can deliver per metre of borehole, and that is a property of the site.

This guide therefore does not publish a price per metre or a borehole total. A rate quoted without the geology, depth, diameter, access and number of holes behind it is not something you can reuse on your site, and the public figures on offer are mostly forum anecdotes rather than sourced rates. What it does give you is the list of things that move the price, the design steps that fix the number of boreholes, the England permissions to check, and a checklist for reading a quote. For the system-level picture, including one published installer guide’s whole-system planning bands, see the cost guide; for the technology itself, see commercial ground source heat pumps.

How a commercial borefield is designed

A borefield design is a chain of inputs, each of which changes how many metres of borehole you pay for. Ask for each of these to be shown in the design, not just the answer.

• Heat load. The peak heat demand and the annual heat energy, from a proper heat-loss calculation and metered fuel use, not floor area. The design also needs the hot water load and any cooling load. If you only have a gas bill, the heat pump sizing calculator gives an indicative figure for screening; it is not a borefield design.
• Ground thermal properties. Thermal conductivity, thermal diffusivity and the undisturbed ground temperature, plus the presence of groundwater flow, set how much heat each metre of borehole can supply. The British Geological Survey sells site-specific ground source heat pump GeoReports that give geology, a borehole prognosis and thermal properties interpreted from the mapped ground, which is a sensible desk step before drilling. It is an estimate, and design reports usually say how much weight they give it.
• Thermal response test. A trial borehole is drilled and fitted with the loop. A heat input is applied to the circulating fluid for a sustained period and the temperature response is logged, from which the effective ground conductivity and the borehole thermal resistance are calculated. It replaces a desk estimate with a measurement for the site. It costs money and time, so ask whether the design relies on one, and who interprets it. Groundwater flow can distort the reading, so the report should say how that was treated.
• Borehole depth and spacing. The loop length needed is divided into boreholes of a chosen depth and laid out at a chosen spacing. Boreholes placed close together interfere with each other thermally over the years, so tight spacing may need more total length; wide spacing needs more land. Depth is bounded by the geology and by the drilling method and regulations, so the same loop length can be a few deep holes or many shallow ones, at different cost.
• Balancing heat. A building that only takes heat out of the ground will cool it year after year, so the borefield must be checked over its whole design life, not only the first winter. Where the building has a cooling load, putting heat back into the ground in summer can rebalance it; if not, the design may need a longer borefield or a different arrangement. Ask to see the long-term ground temperature result.

A design that states only a borehole count and depth, with none of these inputs shown is difficult to challenge. Good practice for ground source arrays is set out in industry standards; the Ground Source Heat Pump Association has published closed-loop vertical borehole standards, and MCS publishes design standards used for the grant scheme. We have not verified which edition or standard applies above the grant size limits, so ask each supplier to name the standard it designs to, in writing.

Drilling and England permissions to check first

These notes describe England and come from GOV.UK; Wales, Scotland and Northern Ireland have their own regulators. Guidance changes, so read the current page before you rely on any of this.

• Closed loop and consents. GOV.UK's open-loop guidance notes that a closed loop heat exchanger needs no groundwater investigation consent or abstraction licence. It also says that from 2 October 2023 you may need an environmental permit for the discharge of heat, so the GOV.UK closed-loop guidance is the first read.
• Exemption conditions. GOV.UK sets exemption conditions for closed loop ground source systems, including that the system is fully sealed and discharges no water or fluid to the environment, that it is not in a groundwater source protection zone 1, and that installing it does not mobilise contamination. The published conditions also set minimum separation distances, for example from protected sites and from private water supplies, so a large commercial borefield may fall outside the exemption and need a bespoke permit; read the current exemption conditions page for the distances. Systems installed before 2 October 2023 are treated differently. A regulatory position statement for a single system serving residential premises exists, but a commercial building should not assume it applies.
• Pollution control. GOV.UK's open-loop guidance also states that boreholes must be designed, constructed and decommissioned in a way that prevents groundwater pollution. For a borefield that means grouting, loop pressure testing and a sealed, recorded finish, which are things to see in the method statement.
• Source protection zones. The Environment Agency publishes groundwater source protection zones. A site inside one is a reason to talk to the regulator before you spend on design. The water source heat pump guide covers the open loop alternative, which has a longer permissions list.
• Planning. In England, Part 14 of the permitted development order has classes for ground source (Class L) and water source (Class M) heat pumps on non-domestic premises, with excavation limited to 0.5 hectares, and Scotland, Wales and Northern Ireland have their own non-domestic classes. Conditions and exclusions apply, so for a commercial site check with the local planning authority, particularly for a large borefield, a plant room or any works near a watercourse. This guide does not give a planning conclusion for any site.

Also check what is below your land before any drill is mobilised: services, tanks, old foundations, contamination and made ground all change drilling method and cost, and a site ground investigation report, where one exists, is worth giving to every bidder.

What moves the price

Without a published rate, the useful question is what changes the total. These are the drivers a commercial scheme should be tested against:

• Total metres drilled. The number of boreholes times depth, which comes from the design above. A weaker ground conductivity or a bigger load means more metres.
• Geology. Hard rock, running sand, gravel, chalk with water or made ground drill at different speeds with different methods, casing needs and risks. Ask what ground the bid assumed and who carries the risk if it differs.
• Access and rig mobilisation. A rig, a water supply, spoil handling and a working area. Tight urban sites or occupied car parks cost more to work in.
• Loop, grout and manifolds. The pipe in each hole, the grout that fills it, the horizontal pipework and chambers linking holes to the plant room.
• Testing and commissioning. The thermal response test, pressure tests and flow balancing.
• Reinstatement. Putting a car park, lawn or yard back, and managing drilling spoil and drilling fluid.
• Plant and connection. The heat pumps, buffer volumes, controls and any electrical supply upgrade are separate from borehole cost, but they are often priced in the same bid. See the sizing guide for how load drives them.

For whole-system scale only: Fuse Energy’s “Commercial heat pump costs” guide, updated 8 July 2026, is a secondary source from an installer. It gives ground source planning bands of £90,000 to £160,000 at 100 kWth and £120,000 to £600,000 for 200 to 500 kWth, including units, controls and integration. Those bands cover the whole system, not the boreholes alone, they are wide and overlap, and they are not a quote. Read them as one published guide’s range, and compare your own bids on the itemised basis below.

What a borehole quote should itemise

When you compare bids, the aim is to see the same list in every one. Ask for the following to be separate lines or clearly stated assumptions:

1. The design basis: peak load, annual heat energy, hot water and cooling assumptions, flow temperature and the standard designed to.
2. Ground data used: desk geology, any thermal response test, and the assumed conductivity and undisturbed ground temperature.
3. Number of boreholes, depth, diameter, spacing and layout drawing.
4. Test borehole and thermal response test: included or provisional, and who interprets the result.
5. Drilling method, casing, grout type and pressure testing, with the permit or exemption position stated.
6. What happens if the ground differs from the assumption: a rate per extra metre, a provisional sum or a fixed risk allowance.
7. Long-term ground temperature result over the design life, including balancing.
8. Pipework, manifolds, chambers, trenching and reinstatement.
9. Heat pumps, controls and electrical supply as separate lines.
10. Maintenance and monitoring, and the warranty on the ground loop itself.

A bid that cannot say what it would charge for an extra borehole is leaving the largest uncertainty with you. If you want quotes to compare, you can send your details; we reply by email. Check any installer’s MCS and other credentials on the public registers before you sign.

Boiler Upgrade Scheme and shared ground loops

The Boiler Upgrade Scheme covers small non-domestic buildings in England and Wales where the applicant owns the building. Per Ofgem installer guidance, a single heat pump is limited to 45 kWth, a multi-heat-pump system serving one property under one voucher to 70 kWth, and a shared ground loop to 300 kWth with each heat pump no more than 45 kWth. The grant is £7,500 for a ground source heat pump; it is £9,000 where the property replaces oil or LPG with no mains gas, to March 2027. Hybrid systems, a heat pump alongside a gas boiler, are not eligible, and a heat pump that has received other public grant funding is not eligible either.

Most commercial borefields will exceed these limits, in which case the scheme does not help. If your design is within them, the drilling cost sits inside an eligible quote, so ask for the ground loop and heat pumps to be priced clearly. The Boiler Upgrade Scheme guide covers eligibility, and for a comparison of ground source with the air option before you commit to drilling, see air source versus ground source.