Coefficient of performance (COP and SCOP)

A COP of 3 means the heat pump gives 3 kilowatt-hours of heat for each kilowatt-hour of electricity. A COP figure is measured at fixed conditions, one outdoor temperature and one water temperature; the real COP changes from hour to hour with the weather. The SCOP, seasonal coefficient of performance, is the yearly heating demand divided by the yearly electricity use over a standard heating season (Regulation 813/2013, Annex I), and it is the figure that matters for the bill.

Data sheets usually give the SCOP for water at 35 °C (underfloor heating) and at 55 °C (radiators). The EU energy label set by Regulation 811/2013 shows a class for each temperature, based on the seasonal efficiency: the SCOP divided by a conversion factor of 2.5, with small corrections.

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