Actually heat pumps work well down to a time when the heat loss of the structure equals the heat output of the heat pump, called the balance point. After the balance point is reached the auxiliary heat, electric or other fuel source, helps supplement the needed heat for the structure. With the heat loss of most RV's that point would be higher than if in a home. The newer heat pumps put out more heat than electricity used even down to zero depending of coarse on their efficiency. Heat pumps also have a defrost cycle that keeps the outdoor coils from freezing, which the Cool Cat does not. Been in the business almost 35 years, wish I had been camping 1/2 that long.
2015 Silverado 2500
Camped 18 nights (not enough )
Retiring in January wait until next year