EER (Energy Efficiency Ratio) – An AC with higher EER means it will give more energy efficiency. SEER (Seasonal Energy Efficiency Ratio). – It is calculated based on the seasonal average, not on the ideal laboratory conditions. A higher SEER value means the appliance will save more energy. HSPF (Heating Seasonal Performance Factor). – It measures the efficiency of the heat pump. AC with higher HSPF means it is more efficient.