These heat pumps work the same as a Stick and Brick Heat Pump, it is the A/C cycle running in reverse.
As the outside temp gets colder, there is less temperature transfer and you will notice the air temperature coming out is not as hot and the unit looses efficiency till finally there is no temperature transfer outside so no heat inside.
Robert & Sheryl
2014 Redwood 38FL
MoRyde 8K IS, Disc Brakes, MoRyde Pin Box
17.5 Goodyear G114's, RV Armor Roof
2018 RAM 3500 DRW, Curt Q24 Hitch