Heat pumps are an energy-efficient alternative to traditional gas-powered furnaces. There are four main types of heat pumps that operate differently due to how they collect heat: water, air, geothermal, and hybrid. Here’s a look at how each type of heat pump works in winter:
Air-to-Air Heat Pump
An air-source heat pump is sometimes thought of like a fridge in reverse. It works by blowing outside air over a network of refrigerant-filled tubes, which causes the liquid refrigerant to warm up and turn into a gas. The gas then runs through a compressor to increase the pressure, making the gas hotter. In the final stage, the hot gases warm up cool water (or air) surrounding a heat exchanger. The hot water and heat then get circulated around your home.
In winter, a common problem is the air-to-air heat pump icing up. Ice builds up because water vapor is generated when energy is drawn out of the air, which then freezes on the pump’s cold metal surface. Ice isn’t a big deal in most cases, as the heat pump has a defrost setting. However, if it’s icing over excessively and affecting the performance of your setup, consider contacting an HVAC professional to come and assess it.
Water Source Heat Pump
As the name suggests, this type of heat pump uses the natural heat present in a water source, such as boreholes, rivers, springs, wells, and ponds. Refrigerant transfers the heat from the water to your home, which travels in either a closed or open-loop system.
With a closed-loop setup, heat exchange coils (or panels) filled with a water-antifreeze mix are submerged in the water source. As the mixture runs through the system, it absorbs the water’s energy and transfers it directly to the heat pump.
Open-loop versions pump water straight from the source to the heat pump. Once the pump extracts the heat, the system pumps the water back to the source.
Water source heat pumps are considered more efficient compared to air-to-air versions, especially in winter. Water temperatures are more stable year-round and heat transfers better in water.
Geothermal Heat Pumps
Also known as a ground-source heat pump, the geothermal heat pump works by harnessing solar energy stored in the ground and extracts it using buried pipework containing refrigerant. The U.S. Department of Energy estimates that the temperature a few feet below the earth’s surface ranges from 45°F to 75°F, depending on the season and latitude. In the winter, the ground is warmer than the air, and it’s the opposite in the summer. Geothermal heat pumps utilize these pleasant ground temperatures to provide heating in the winter and cool air-conditioning in the summer.
One question you might wonder is: Should I turn off my heat pump in extreme cold? It’s worth turning off your heat pump and swapping to an alternative heat source if the air or water temperature drops to between 25°F and 40°F as heat pumps become less energy efficient at this point. You can still run your heat pump below 25°F, however, it becomes costly as the system requires more energy to function. The advantage of a geothermal setup is that the pipes and heat exchanger are buried underground and thus protected from the cold.
Hybrid Heat Pump
Hybrid systems use a heat pump source, like air or geothermal, and combine it with one or more additional heating methods, such as a gas furnace or electric boiler. The primary benefit of this setup is that you have a backup heat source if the heat pump fails, which is especially useful in winter.
If you’re thinking of installing a heat pump or have questions about your current heating system, you can contact our team of expert HVAC technicians to discuss your options. In the meantime, check out our handy guide covering the Do's and Don'ts of Heat Pumps in the Winter if you want to learn more about how to best care for your heat pump in the winter.