A closed-loop borehole may offer anything from 3-7kW but this depends on many factors including the depth of the borehole, materials installed within the borehole and the thermal conductivity of the surrounding rock. It’s important to determine the required load for the GSHP first, as this will then help dictate what the specification of the borehole(s) should be. A qualified designer/installer (alongside the drilling contractor) will be able to carry out the heat loss calculations to establish the required load of the GSHP. In turn, this will inform the project team how much drilling will be required.