Two exterior residential heat pumps buried in snow
December 21, 2018

At Goggin Energy, we get a lot of questions from homeowners about heat pumps — including energy efficiency and maintenance. Whether you’re considering a heat pump for your home in southern Maine or already own one, it’s important to understand the defrost cycle of a heat pump — and how issues with the defrost cycle can affect the efficiency and functionality of your heat pump system.

What Is the Defrost Cycle?

Heat pumps pull ambient heat from outside air, compress it, and transfer it indoors to keep your house warm—even here in Maine when temperatures are often below freezing. Once outside temperatures reach the 30s, it’s common for moisture in the air to freeze on the surface of the outdoor coil.

That’s where the defrost cycle comes in. Heat pumps have a defrost cycle to melt any frost that accumulates on the outdoor coil. During the cycle, the heat pump runs in reverse (in cooling mode) for 30 seconds or up to a few minutes—just long enough to remove accumulated frost on the outdoor coil. Most outside units have built-in timers which determine how often the unit goes into a defrost cycle, such as every 60 or 90 minutes.

What Happens If a Heat Pump Does Not Defrost Correctly?

Without proper defrosting, accumulated frost and ice on the outdoor coil would interfere with the operation of the heat pump, forcing it to work harder and reducing its efficiency. The outside unit could also become damaged or non-functional due to heavy ice accumulation.

Alternatively, some heat pumps defrost more often than they need to. This is especially common with older heat pump systems which may operate even when there is no frost on the outdoor coil. Frequent defrost cycles could be a sign that the ducted heat pump or ductless heat pump (mini-split) is undersized for the area it serves. It could also be a sign that the heat pump system has not gotten the maintenance it needs.

Get Answers to Your Heat Pump Questions

Understanding the defrost cycle of a heat pump can help you identify when your heat pump is operating as it should — and when there may be an issue that requires a repair. If you have questions about your current heat pump system or would like to know more about how a new heat pump might operate in your home, talk to the Goggin Energy team. Our goal is to help you feel comfortable at home no matter the season, and as southern Maine’s premiere authority on heat pumps, we’re here to answer your questions.

Have questions about how heat pumps operate or when it may be time for a repair? We have answers. Call


or contact us to talk to the team at Goggin Energy.

Heat pump covered in ice?

Learn more about the defrost cycle.


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