ABOUT HEAT PUMPS
Heat pumps don’t create heat in the same way that a fuel-burning appliance does. They do need electricity (or another fuel source) to operate, but they can produce several times as much heat energy as the electricity they consume. However, a heat pump’s ability to extract heat is not unbounded; at some point it can get cold enough outside that air-source heat pumps become unable to maintain the indoor temperature (balance point). Although the relevant outdoor temperature may vary depending on the heat pump design, this rule applies to every air-source heat pump.
Ground-source heat pumps are among the most expensive mechanical systems to install, but they provide heating and cooling, so the higher cost is a little easier to swallow. Air-source heat pumps are more affordable than ground-source heat pumps.
Air-source versus ground-source
There are two basic kinds of heat pumps used for residential space heating: air-source heat pumps and ground-source (sometimes called geothermal) heat pumps. Ground-source heat pumps can be open-loop or closed-loop systems.