Heat pumps consume electricity to move heat around, moving heat from outside to indoor spaces to create warmth or vice versa to cool inside spaces. Heat pumps are alternatives to furnaces and air conditioning units, providing four times more energy than what they consume. They work best in moderate climates. The Heating Seasonal Performance Factor (HSPF) and Seasonal Energy Efficiency Ratio (SEER) are needed to calculate electricity savings of heat pumps.
Identify the HSPF for the heat pump. The HSPF is a ratio that compares heating capacity to electricity usage. It is calculated by dividing the total space heating required during the heating season (expressed as in British Thermal Units, Btus) by the total electrical energy consumed by the heat pump during the same season (expressed as kilowatt hours, KWh). The HSPF is calculated by the heat pump manufacturer and is included on relevant energy labeling, specifically the EnergyStar label.
Identify the Seasonal Energy Efficiency Ratio (SEER) for the heat pump. The SEER is a ratio describing cooling performance. It is calculated by dividing the total heat removed from a space during the cooling season, expressed in Btus, by the total electrical energy consumed by the pump during the cooling season, expressed as kWh.
Interpret the HSPF number. HSPF rates the efficiency of the compressor and electric resistance elements in the pump, all of which increase energy costs. For example, more voltage is needed to overcome resistance. Some utility rate structures charge for increases in voltage. A more efficient heat pump will need less voltage. Typically, an HSPF between 8 and 10 is most efficient.
Interpret SEER number. Higher SEER numbers indicate less electricity consumption by the heat pump. If you replace a heat pump with a SEER of 6 with a heat pump with a SEER of 12, you will use half as much electricity for the same amount of cooling, cutting your costs in half. The most efficient heat pumps are those with SEER numbers between 14 and 18.
Calculate electricity savings. Compare HSPF and SEER factors for the old and new heat pump. Extrapolate the numbers to your utility bill. In step four, a heat pump with a SEER of 12 uses half as much electricity as the older pump with a SEER of 6. Add up your electricity costs for the past cooling season, as found on your utility bill, and multiply the cost by $.50 to indicate savings associated with a new heat pump.