Comment by nitsuaeekcm

The best mental model for a heat pump is that they can maintain a certain temperature differential, say 80F. If it gets to be 0F outside and you want it to be 70? You don’t need to switch to a fully separate heating system, you just need to warm up either the incoming or outgoing air an additional 10 degrees via a small resistance heater. The super wide range heat pump systems will do that automatically, and the principle really applies to any differential you could want.