Ground Source Heat Pumps: What You Need to Know About Boreholes and Trenches

Ground source heat pumps are the most efficient heating systems available, but they require significant groundwork. The two main installation methods - boreholes and horizontal trenches - suit very different properties. Here's what each involves.

Horizontal trenches

The more common method for homes with large gardens. Pipes are laid in trenches typically 1.2-1.8m deep and spaced 1.5m apart. The total trench length depends on your heating demand - a typical 3-bed house needs about 100-150m of trench.

What to expect:

• Trenches dug across your garden (major disruption for 2-3 days)
• Pipes laid in the trenches, connected to the heat pump


• Trenches backfilled and garden reinstated


• Garden recovers within one growing season


• You can't build permanent structures over the loop area

Cost: £15,000 - £25,000 total (including heat pump)
Space needed: 200-400m2 of garden

Boreholes (vertical loops)

For properties without enough garden space, boreholes go straight down. A drilling rig bores one or more holes 60-150m deep, and a closed-loop pipe is inserted into each.

What to expect:

• Drilling rig arrives (needs access for a medium-sized truck)
• Each borehole takes 1-2 days to drill


• Most homes need 1-3 boreholes depending on heating demand


• Less garden disruption than trenches but the drilling is noisy


• Geology matters - rock is harder to drill through than clay

Cost: £20,000 - £35,000 total
Space needed: Much less - each borehole needs just 2-3m2 of access

Which method is better?

For most homes with adequate garden space, horizontal trenches are the cheaper and simpler choice. Boreholes are the solution when garden space is limited but budget allows.

After the BUS grant

Both methods qualify for the £7,500 Boiler Upgrade Scheme grant. After the grant:

• Horizontal system: £7,500 - £17,500
• Borehole system: £12,500 - £27,500

Compare that to an air source heat pump at £2,500-7,500 after grant. The cost difference is substantial, which is why ASHPs dominate the market despite GSHPs' efficiency advantage.

Is ground source right for you?

Ground source makes most sense for:

• New builds (groundwork is far cheaper during construction)
• Rural properties with large gardens


• Homes with high heating demand


• Properties where you plan to stay 15+ years

For everyone else, an air source heat pump delivers 80% of the benefit at 40% of the cost. Compare quotes for both types and see what installers recommend for your specific situation.