Heat pump performance is measured in Coefficient of Performance (CoP). This is the ratio of units of heat output for each unit of electricity used to drive the compressor and pump for the ground loop. A CoP of 4 means that for every kilowatt of electricity put in, 4 kilowatts of energy out in the form of warm water are achieved. Put simply, a ground source heat pump can provide up to 3 kilowatts of free energy for every 1 kilowatt of electricity used to power it, giving a CoP of 4.

Performance is reliant on a range of factors and can vary so it is now common practice to state an estimated Seasonal Performance Factor (SPF) rather than a best-case scenario. This reflects seasonal variations and is a more realistic indicator of performance.

The GSHP Association states:

“Most electricity suppliers are now offering ‘clean green’ electricity from a renewable energy source and, if you use this to power your heat pump, your property will be totally heated from renewable energy with zero carbon emissions.” (Source: www.gshp.org.uk/faqs.htm ).