A heat pump works similarly to an air-conditioner except it can move air in two directions — into the home and out of the home — being a furnace and an air conditioner all in one. An air-source heat pump (also called an air-air heat pump) extracts heat from the air outside your home and pumps it inside through coils that contain refrigerant. Beside the coils, the pump unit has two fans, a compressor and the key to making the unit both a heater and an AC — a reversing valve. Very well-insulated homes, even in frigid New England, can be heated almost entirely with a heat pump due to advancements in this technology that allow air-source heat pumps to extract heat from the air to about 15 degrees Fahrenheit.
Besides the basic air-source heat pump, there is also a ground-source (geothermal) heat pump. Ground source heat pump systems extract heat from deep in the ground rather than from outside air. The advantage to air-source heat pumps is that they are far less expensive to install compared to ground source heat pumps, and they can do the same job.
Air-source heat pumps either connect to a whole-house duct system or are installed in an exterior wall to serve a particular room or house section. The latter are called ductless mini-split heat systems. The main advantages of mini splits are their small size and flexibility for zoning or heating and cooling individual rooms. If you have a particular room or house section that you want to make more comfortable, a mini-split may be the ideal solution.
I was visiting a professional office in Newburyport recently where it was cooler than normal inside. I noticed it was heated with electric baseboard, which is why the thermostat was set low — electric heat is expensive. This situation represented a perfect example of where a low-cost mini-split heat pump could be installed to cut the electric bill by about two thirds. Rebates from utilities provide additional incentives and help subsidize the installation of air-source heat pumps.