How is efficiency rated for geothermal?

Heating and cooling systems carry an efficiency rating which is certified by the Air-Conditioning, Heating, and Refrigeration Institute (AHRI). Fossil fuel furnaces use AFUE. Air conditioners use SEER while heat pumps use HSPF and SEER.

Geothermal heat pumps rate heating efficiencies according to their coefficient of performance, or COP. It’s a scientific way of determining how much energy the system produces versus how much it uses. Most geothermal heat pump systems have COPs of 3-4.5. The WaterFurnace 7 Series holds the highest recorded certified performance of 5.3 COP in a closed loop and 5.9 in an open loop. That means for every dollar of energy used to power the system, up to $5.90 of energy are supplied as heat. Where a fossil fuel furnace may be 78-98% efficient, a geothermal heat pump is over 500% efficient.

For cooling, geothermal units are rated in Energy Efficiency Ratio (EER). This is a measure of the instantaneous energy efficiency of cooling equipment. The higher the EER, the more efficient the unit. The WaterFurnace 7 Series carries a certified rating of 41 EER for closed loop and 53.2 EER for open loop. This is more than twice as efficient as any traditional heat pump or air conditioner and a third higher than any other two-stage geothermal heat pump.