"As far as the efficiency of heat pump is concerned, the coefficient of performance (COP) is the measure of heat pump’s efficiency. It is determined by dividing the energy output of the heat pump by the electrical energy that is required to run the heat pump at a specific temperature. Hence, higher is the COP more efficient is the heat pump. The heating seasonal performance factor or HSPF on the other hand is the measure of the total heat output in Btu of a heat pump over the entire heating season divided by the total energy divided in watt hours it uses during that time. The energy efficiency ratio or the EER measures the cooling capacity of the heat pump. It is determined by dividing the cooling capacity of the heat pump divided by the electrical energy inputs at a particular temperature. The higher is the EER rating, more efficient is the system. The seasonal energy efficiency ratio on the other hand measures the total cooling offered by the heat pump over an entire season. "