Energy Efficiency Ratio (EER) - a ratio calculated by dividing the cooling capacity in Btu per hour by the power input in watts at any given set of rating conditions. Heating Seasonal Performance Factor (HSPF) - the total heating output of a heat pump during its normal annual usage period for heating divided by the total electric power input in watt-hours during the same period. Seasonal Energy Efficiency Ratio (SEER) - the total cooling capacity of a central unitary air conditioner or unitary heat pump in Btu's during its normal annual usage period for cooling divided by the total electric energy input in watt-hours during the same period.