Ground source heat pump costs after the grant

The 2026 numbers

A domestic ground source heat pump installation costs £18,000 to £35,000 fully installed at 2026 prices, before support — and beyond £40,000 for large properties on deep boreholes. Subtract the £7,500 Boiler Upgrade Scheme grant (identical to the air source grant, with 0% VAT until 31 March 2027) and the realistic after-grant range is £10,500 to £27,500. The spread is driven almost entirely by one question: how does the heat get out of the ground?

• Horizontal ground loops (trenches) — the cheaper collector, £18,000–£26,000 installed before grant, needing 600–1,200 m² of diggable land. After grant: £10,500–£18,500.
• Vertical boreholes — £25,000–£35,000+ before grant, with drilling at £25–£45 per metre and most homes needing one to three holes of 60–200 metres. After grant: £17,500–£27,500+. The footprint is a few square metres, so boreholes suit homes with small gardens and large heat demands.
• Shared ground loops — for flats and new developments, one borehole field serves many dwellings, each claiming the full £7,500. Per-dwelling costs approach air source territory, which is why this model is growing fast in social housing.

Where the money goes

Roughly a third of a GSHP budget is the heat pump, cylinder, controls, and internal hydraulics — the same scope as an air source install, covered on the ASHP cost page. The remainder is ground works: excavation or drilling, collector pipework and brine, reinstatement of the garden or drive, and the design work (a thermogeological assessment for boreholes) that ensures the collector can feed the load for fifty years without freezing the ground around it. That collector is also the part with the extraordinary lifespan — loops and boreholes are routinely rated for 50–100 years, meaning the next heat pump you buy in the 2040s connects to ground works you have already paid for.

What you get for the premium

Stability. The ground at collector depth holds 8–12°C every day of the year, so a GSHP delivers seasonal performance factors of 4.0–4.5 — each kWh of electricity becoming over four of heat — and does it on the coldest night of January, exactly when an air source unit's efficiency dips. There is no outdoor fan unit (the silence suits conservation areas and tight terraces), no defrost cycles, and less mechanical wear. At 2026 electricity prices, the efficiency edge over a good ASHP is worth £150–£250 a year on a typical larger-home heat demand; on oil or LPG replacement the total running-cost saving is dramatically larger, as the running-costs comparison sets out.

Who should — and shouldn't — buy ground source

The strong cases: larger homes with heat demands above ~20,000 kWh, where the efficiency premium compounds; off-gas-grid properties replacing oil or LPG, where running-cost savings are largest; self-builds and major renovations, where diggers are on site anyway and trenching is cheap; and multi-dwelling projects on shared loops. The weak case is the ordinary gas-heated semi, where the after-grant premium over air source rarely pays back — and we say so plainly rather than upselling the bigger ticket. Whichever side you land on, the grant conditions are identical and the eligibility page covers them; the BUS guide explains the voucher process, which allows six months for ground source precisely because of the civil works.