How Much Land Do You Need for a Ground Source Heat Pump?

The short answer

For horizontal collectors, plan on roughly 2.5 times the heated floor area of the house in open, diggable ground — about 375 m² for a 150 m² home — trenched at around 1.2-1.5 m deep. Slinky coils fit the same pipe length into shorter trenches. Vertical boreholes need almost no surface area but do need drilling-rig access, typically 90-150 m of depth per borehole.

Horizontal trenches

Straight pipe in parallel trenches is the cheapest collector per metre and the most land-hungry. It suits farmsteads, smallholdings and rural plots with a paddock or field. The ground must be genuinely available: not under a drive you need, not where an extension is planned, and clear of drainage runs and services. Reinstatement matters too — the grass comes back, but the first season looks like groundworks.

Slinky coils

A slinky is the same pipe coiled in a long spiral, so a given collector length fits a shorter trench. It is the usual Cornish compromise where there is land but not enough length for straight runs. Trench depth stays similar; the pipe count per metre rises.

Vertical boreholes

Boreholes trade surface area for drilling cost. Two or three holes of 90-150 m, spaced several metres apart, will serve a typical house and leave the garden intact — which is why boreholes are the answer for small plots, and often the only ground-source option in a town. You need access for a rig, somewhere for arisings, and a sensible route for the manifold pipework back to the plant room.

Cornish granite changes the borehole maths

Much of Cornwall is granite and metamorphic killas rather than soft sediment. Drilling hard rock is slower than drilling clay, which is why borehole quotes vary more between properties here than in most of England — the geology under your garden, not a national average, sets the price. The upside is that hard rock conducts heat well once you are into it, so the depth needed per kW can be lower than a generic figure suggests. The Eden Project's geothermal well at Bodelva, drilled to around 4.5-5 km, is the same principle at industrial scale.

Costs and the grant

In Cornwall, the ground array is usually £6,000-£14,000 for trenches or slinkies including groundworks, or £12,000-£22,000 for boreholes, on top of £11,500-£16,800 for the heat pump, cylinder, controls and commissioning — so £18,000-£32,000 before grant for a complete installation. The Boiler Upgrade Scheme pays the same for ground source as for air source: £7,500, or £9,000 until March 2027 where you are replacing oil or LPG and have no mains gas connection. Since the grant no longer favours air source, the choice is about land, disruption and how long you will own the house.

Ground source is also the easier planning route: it sits in its own class in Part 14 of the GPDO with none of the size, siting or noise limits that apply to an air source unit, which matters on a listed property, in a conservation area, or inside the Cornwall and West Devon Mining Landscape World Heritage Site.

No land? Read this first

If there is no diggable ground and no rig access, air source is the sensible answer rather than a compromised ground array — one outdoor unit, the same grant, half the installed cost. Our page on ground source heat pumps Cornwall sets out loops, costs and process in full, and heat pumps Cornwall covers the air source route and the county coverage map.