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Geothermal Heat Pump Theory

Efficiencies of Heat Pumps

The efficiency of a heat pump depends upon the temperature at which it finds its heat (source temperature) and the temperature at which it discharges this heat (sink temperature). The greater the difference between the source temperature and sink temperature, the more work is done by the compressor in the heat pump; and consequently, the more cost.


In other words, as the source temperature declines, so will the efficiency of the heat pump. The prospective buyer will naturally choose the type of heat pump (air source vs. ground source) which gets its heat from the source that remains at the highest temperature for most of the year.


During the heating season in our part of Canada, our mean ground water temperature will remain 47°F (8°C) where the mean winter air temperature is approx. 12°F (-10.4°C). It is for this reason that seasonal efficiencies of a ground source heat pump are much higher than an air source.