You might need to experiment. What sort of thermostat do you have? Ecobee lets you see one single chart which type of heat is being used and the outside and inside temperatures.
From there you can adjust what temp to skip heat pump and go straight to aux heat so that you aren't wasting time and energy without making your home any warmer. It will automatically switch over of course if no temperature increase is detected within a set amount of minutes (programmed with some sane defaults of course).
I have a dual system and part of it was replaced more recently. I found the part of it that's newer can heat effectively at lower temps. They aren't the same model or anything though.