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My unit has both a heat pump and gas furnace. Of course the heat pump is used for cooling in the summer. In the winter the thermostat is set to use the heat p
by lizknope 4y ago
My unit has both a heat pump and gas furnace. Of course the heat pump is used for cooling in the summer. In the winter the thermostat is set to use the heat pump for heating until it is below 40F. Below that and it switches to natural gas. The company that installed it and maintains it said that was the best crossover point for efficiency and cost. I didn't look at any specific cold weather heat pumps that are still efficient below freezing.
- cpncrunch 4y agoAll heat pumps are generally still efficient at well below freezing, and will have a COP (efficiency) above 1 even at -15C. The problem is that they don't generate a huge amount of heat at those ambient temperatures, so you need a backup source of heat. A heat pump should be able to keep your house at room temperature when the outside temp is around freezing, but it will take a long time to heat up your house if you let the temperature drop overnight. 40F seems unusually high for your aux heat set point, unless you have expensive electricity and cheap gas.