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Heat Pump efficiency with outdoor temperature?
I have a relatively new (2 years) air-to-air heat pump in an old house (1928) .
How do I determine at what outside temperature I turn the heat pump off and turn on the propane heaters in the house? I do not want to energize the supplemental electric resistance heat in the heat pump due to its high cost.
Is there a moderate winter temperature range in which it would be wise to run both the heat pump and the propane heat? The propane heaters are a faux woodstove in the living room with variable flame, and non-vented wall units with built in thermostatic control (on-off) in other rooms.