Can it be used in very cold climates?

How does geothermal heating work in a cold climate? I’ve heard that geothermal heat pumps can be very efficient but don’t work well in cold climates.

Answer from Green Energy Efficient Homes

It’s true that heat pumps can be very efficient, but that air exchange heat pumps are not very efficient in really cold climates. But don’t confuse air exchange heat pumps with geothermal heat pumps.

How does geothermal heating work compared to air exchange heat pumps? For geothermal heating, a liquid, usually a combination of antifreeze and water, circulates in a large loop of tubing that has been either buried in a bed several feet under ground (horizontal loop), or placed in a deep bore hole drilled for that purpose (vertical loop). A second loop of tubing, containing a refrigerant liquid such as Freon, gathers heat from the ground source loop and sends it into the home. The geothermal heat pump is the device that extracts and concentrates the heat from the ground source loop and places it in the second loop so it can warm your home.

Geothermal HVAC system control panel

Geothermal HVAC control panel
Photo by jblyberg, via FLICKR

An air exchange heat pump works on a similar basis but instead of having a second geothermal loop buried under ground, an air exchange heat pump just draws heat out of the outside air. This is much cheaper to install, but unfortunately the air is very cold in cold climates in winter, so the amount of electrical energy the heat pump expends trying to extract heat from very cold air is almost as much as the heat energy it manages to extract. In other words, on a very cold day, air exchange heat pumps are not really any more efficient than energy saving space heaters.

How does geothermal heating work to get around this problem? Simple. A geothermal heat pump extracts heat from the ground – between several feet down and hundreds of feet down (depending on whether it’s a horizontal or vertical loop) – so that it’s extracting heat from a place that is actually reasonably warm. The warmer the heat source (and yes, that really cold winter air is a heat source), the less energy from the heat pump is required to draw heat out of the heat source.

For this reason, geothermal heating systems are great for really cold climates, while air exchange heat pumps are only suitable for climates where the temperature doesn’t fall much below freezing, or doesn’t fall well below freezing more than a few days a year.

Green Energy Efficient Homes articles cited

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