[toomuchtodo]

Air source heat pumps can operate all the way down to 0F. I’ve paired one with a hydronic system, with a firewood heated boiler for backup heat, in rural Pennsylvania.

The less reliable power is and the colder it gets during winter months, the more tricky the problem gets.

[brudgers]

Typical residential units come with a resistance electrical heating element. It forms the basis of the "emergency heat" functionality. It also begins operating as ambient outdoor conditions exceed the performance of the heat pump mechanism.

I mention this not because this is what your particular system does. I mention it because it is typical for widely available residential heat pumps in the ordinary market.