@teknomunk @hazlin @BowsacNoodle @sickburnbro @jeffcliff @skylar The typical COP for a heat pump is calculated at a pretty modest temperature differential and it's only accurate at that operating point.

The greater the difference between the outside temperature and the temperature you're trying to maintain inside the worse the COP gets which means in extreme conditions when you need them they most are the worst conditions for them in terms of energy efficiency.