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Efficiency

In general, efficiency is defined as the Useful Work or Energy Delivered divided by the energy supplied to do that work.

In heating and cooling with heat pumps, the definition is changed somewhat. For cooling the efficiency is expressed as the Energy Efficiency Ratio - EER.

If the unit cooling capacity and EER is known, the kW power input can be calculated. For example, a unit having a total cooling capacity of 26,000 BTUH at an EER of 11.4, the cooling unit power input is:

For heating, the efficiency is expressed as the Coefficient of Performance or COP.

If the unit heating capacity and COP is known, the kW power input can be calculated. For example, a unit having a heating capacity of 33,500 BTUH at a COP of 3.9, the heating unit power input is:

Keep in mind the unit EER and COP are dependent on the entering ground water temperature, water flow rate through the unit, airflow rate and the entering air temperature. High efficiency equipment comes with a higher price tag.

It is difficult to state a general rule about selecting equipment on the basis of efficiency because of the economic considerations and the merits of each system and the equipment used with it.