How much garden do I need for a ground source heat pump?

For horizontal ground loops, you typically need 2-3 times the floor area of your home. A 10 kW system might need 400-600 m² of garden for horizontal trenches at 1.2m depth. Vertical boreholes need much less surface area (around 25 m² per borehole) but cost more to drill. Boreholes are often the only option for smaller gardens.

What COP can I expect from a ground source heat pump?

Ground source heat pumps typically achieve a seasonal COP of 3.5-4.5, meaning they produce 3.5-4.5 kWh of heat for every 1 kWh of electricity consumed. COP depends on ground type, loop design, and the flow temperature required. Lower flow temperatures (35°C for underfloor heating) give higher COP than higher temperatures (55°C for radiators).

How much does a ground source heat pump system cost?

Typical installed costs range from £15,000-£25,000 for a domestic GSHP system including ground works. Horizontal ground loops are cheaper (£2,000-5,000 for trenching) while vertical boreholes cost £6,000-12,000 or more. The UK Boiler Upgrade Scheme (BUS) offers a £7,500 grant towards GSHP installation costs.

Is a ground source heat pump better than air source?

GSHPs are more efficient (COP 3.5-4.5 vs 2.5-3.5 for ASHP) because ground temperatures are more stable than air temperatures. They are quieter with no external fan unit. However, they cost more to install due to ground works. GSHPs are better suited for new builds or properties with adequate garden space.

What ground type is best for a GSHP?

Wet clay and rock provide the best thermal conductivity and heat extraction rates. Wet clay extracts around 35 W/m for horizontal loops and 55 W/m for boreholes. Dry sand is the poorest performer at around 25 W/m horizontally. A ground thermal conductivity test can determine the exact extraction rate for your site.

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Ground Source Heat Pump Calculator — GSHP Sizing

Size a ground source heat pump system for your property. Calculate ground loop length, borehole depth, COP, running costs, and savings versus a gas boiler.

Property Heat Loss

From heat loss calculation or EPC

Hot Water Demand

Based on number of occupants

Available Garden Area

Accessible area for ground works

Ground Type

Soil or rock type in your area

Loop Type

Horizontal needs more space, vertical costs more

How We Calculate This

This calculator sizes a ground source heat pump system based on your property heat loss and the thermal properties of your ground conditions. It estimates loop length or borehole depth needed to extract sufficient heat from the ground.

System sizing

Heat pump capacity: Based on property heat loss plus hot water demand, rounded to nearest common unit size
Ground extraction: The heat pump extracts heat from the ground equal to output minus electrical input (output x (1 - 1/COP))
Loop length: Total extraction needed divided by the ground-specific extraction rate (W/m)
COP estimation: Based on loop type, ground conditions, and required flow temperature

Cost comparison

Running costs are compared against a gas boiler at the specified efficiency. The calculation uses annual heat demand (capacity x running hours) divided by COP to determine electricity consumption.