Heat pumps transfer heat from one place to another—providing both heating and cooling. They work on the fundamental principle that heat exists in air even at extremely low temperatures. In the winter, a heat pump extracts heat from outside air and delivers it indoors. To cool a house on hot summer days, it works in reverse, extracting heat from room air and pumping it outdoors.
Heat pumps give off less heat at one time than a conventional gas furnace. This means they offer a mellower type of heat, stay on longer and circulate more air throughout the house. They’re controlled by the same type of thermostat used for forced-air systems. On really cold days a heat pump must work especially hard to collect heat—that’s when the supplemental heater switches on to boost warmth. Some heat pumps can heat your water, too. New thermal storage units even store heat and cold, collecting it during non-peak hours for peak-hour use.