Heat pumps are an option on many motorhomes. All they really are is extra mods made to the existing air conditioners. In effect, the heat transfer is backward and the heat from the “outside” is being pumped or transferred, to the “inside”.
Heat pumps are not a very efficient method of heating. But, when it isn’t all that cold out and you have shore power available, it can be a source of free heat. Heat pumps also work on a temperature differential and their basic inefficiency makes it even tighter than when cooling.
Heat pumps do not work in cold temperatures. Once it gets down to 40 degrees you’ll be hard-pressed to get the coach warmed up too much more than 60 degrees inside.
As the temperature outside drops even further, so does your ability to heat the interior. Furthermore, you can damage the compressor when running at low temps. The oil in the compressor is designed to lubricate it at high ambient temperatures when it’s hot outside. Accordingly, it must be a pretty thick lubricant to keep it from breaking down in the heat. That same heavy viscosity works against it when the temps go down and the oil gets very thick.
Running in the heat pump mode at very cold temperatures is not only inefficient but damaging to the compressor. For this reason, heat pump manufacturers put low-temperature cutoff switches on their systems. Typically these will prevent operation below 40 degrees.