While they always offer energy savings over straight electric heating, as the outside air gets colder, they become less efficient. In climates with mild winters, heat pumps may provide cost-effective heating when compared with fossil fuel furnaces, depending on the relative costs of electricity and natural gas. Heat pumps should be carefully sized for the application. Over-sizing results in reduced energy performance, inferior humidity control and shorter equipment life due to equipment short cycling. One of the overall benefits of choosing a heat pump over another heating source is that the air conditioning capability is built-in, rather than having a furnace as well as separate air conditioning equipment.
Energy use depends on operating conditions for both the heating season and the cooling season.
Estimating annual energy use by a heat pump is extremely difficult without the use of a computer simulation that models loads on the unit for every hour of the year using average hourly weather data. FEMP has established minimum recommendations for equipment performance. For additional details on these efficiency recommendations, see For Additional Information below. The table below shows results from a FEMP analysis performed for a 10- ton heat pump. Cost savings would be higher if the price of electricity is higher.