Ground source pumps work similarly to Air Source but collect he heat from pipework buried in the ground. By all accounts it is amongst the cheapest and most efficient forms of heating available but requires perhaps the most work/cost for installation compared to other technologies.
Ground source systems use an internal unit with a compressor that makes little more sound than your fridge and will sit quite happily in a kitchen or utility room if required. Heat is collected from either ground loops (horizontal lengths of pipe buried around 1.5m deep in the ground) or from boreholes (specialist hole drilled into the nearby ground).
Boreholes offer a compact and easy solution but can be expensive, whereas ground loops tend to be cheaper but require sufficient land area and contractors to dig in. Both give almost constant feed of temperature to the pipes (around 10°C) all year round which is then fed to the Pump to be turned into usable heat for the system.
This makes them extremely efficient and able to be tuned to this temperature (unlike air source pumps) giving impressive efficiencies of 400% – 500%+ (i.e. 1 Kw of electricity produces 5Kw of heat).
Like Air source pumps, ground source systems work best when the temperature rise is minimal – so again underfloor heating systems and oversize radiators offer significant gains in efficiency. They can work with traditional radiators and still prove effective so it’s important to consider your heating emitter design along with your heating system options if you have a choice.
Combine this with an RHI rate almost double that of Air source systems and these systems offer incredible performance and rewards. Possible downsides are of course initial investment costs and the need for land or expensive boreholes.
If you have applied in the past with no success you may be accepted now as the qualifying criteria was changed dramatically at the beginning of the year (2017) to help more households pass for free funding.