Field measurements of ground source heat pump systems installed in existing single family houses - Evaluation after several years of operation.

Twenty Swedish ground source heat pump systems in single-family houses have been monitored during two years by SP on behalf of the Swedish Energy Agency. The houses were built between 1940 and 1979 and the heat pumps were installed during 2001 – 2007. The total heat supplied to space and domestic hot water heating differs considerably between households. The first year was colder than the second year which was shown to have an impact on the SPF, the Seasonal Performance Factor. The results from the two years of measurement showed SPF values between 1.9 and 3.5 (average 2.7) for the first year and for the second year, the SPF ranged from 2.1-3.6 (average 2.9). The energy coverage ratio ranged from 93% to 100% during the second year. There was no obvious sign of a deteriorated performance of the heat pump systems after several years of operation.