Measuring Geothermal Heat Pump Performance

COP (Coefficient of Performance)

The ratio of heating provided by a heat pump to the energy consumed by the system under designated operating conditions. The higher the COP, the more efficient the system.. The key measure is not the COP at any one moment, but the average COP over the heating season. This is referred to as the seasonal performance factor (SPF).

EER (Energy Efficiency Ratio)

Like the COP, the EER is the ratio of the cooling output to the energy consumed by the system. The higher the EER, the more efficient the heat pump. The average EER over the cooling season is referred to as the Seasonal Energy Efficiency Ratio (SEER).

Most geothermal heat pump systems have COPs of 3-4.5. That means for every unit of energy used to power the system, 3-4.5 units are supplied as heat. Where a fossil fuel furnace may be 78-90 percent efficient, a geothermal heat pump is about 400 percent efficient. Integrating a GHP with solar hot water collectors, optimizing flow rates, and running GHPs at partial loads all lead to significant increases in the COP of the GHP and are being implemented in EEC's platinum LEED home.

Figure courtesy of Waterfurnace

Comparison of heating and cooling efficiencies of GHPs with conventional systems Figure courtesy of Waterfurnace

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