What is a Heat Pump:

What is a Heat Pump?

We’re asked this question a lot. In the Southern United States, air source heat pumps are the dominant source of home heating and cooling in a single system. However, in colder climates, they are not as well known.

The technology in an air source heat pump is similar to what you would find in your kitchen refrigerator. Using a simple refrigeration cycle, refrigerators remove heat from your food and drinks and reject it into the kitchen. This is why the coils on the back of your refrigerator will feel warm. This process of moving heat is achieved by taking advantage of the energy stored and released when a refrigerant changes from a liquid to a gas.


Simply put, a heat pump can move heat into or out of your home. In the summer time, it acts just like a standard air conditioner and moves heat from inside your home to the outdoors. It does exactly the opposite in the winter; it captures heat from the outdoors and moves it into your home, keeping you and your family warm.

How does it get heat from cold outside air? Heat is molecular motion in the air. The temperature at which molecular motion stops, also known as Absolute Zero, is -459°F. That means that, even at -30°F, there is plenty of heat in the air that we can take advantage of.

The properties of the refrigerant used in a heat pump are such that it evaporates (changes from a liquid into a gas) and condenses (changes from a gas to a liquid) at much lower temperatures than water. In terms of the refrigeration cycle, this means that we can take advantage of these phase changes to store and transport this heat energy into your home.

A heat pump looks just like a central air conditioner and most of the components are the same. On the inside of the home, you’ll see an air handler attached to ductwork. On the outside of the home, you’ll see the outdoor unit. Running between the outdoor unit and the air handler is a pair of copper pipes called a ‘line set’. These are the pipes through which the refrigerant travels between the outdoor unit and the air handler.

Heat pumps have been known for a long time to provide clean and efficient heating in climates that do not experience prolonged periods of temperatures below 30°F. The efficiencies of a heat pump are hard to beat; when they are running with only the refrigeration cycle, they operate above 100% efficiency. In the case of the Acadia™, we maintain operating efficiencies above 200% at outdoor air temperatures as low as -15°F. This means that for every unit of electrical energy you put into the Acadia™, you get out two units of heat energy. Compare that to a fossil fuel system running at 94% efficient. For every 1 unit of fossil fuel energy you burn in your furnace, you’ll only get 0.94 units of heat energy out. Please see the Acadia™ vs. Fossil Fuel page on our website for more comparisons.