Hi mena,
Heat pumps draw about 1200 watts. However they extract 13500 btu's of heat. A similar sized resistance heater would only output about 3600 btus.
The rub is, that below about 6 c (40 f) output from the heat pump starts to drop. So just when you need the most heat, efficiency goes down. By 0 c (32 f) they are barely better than resistance heating. The most modern ones will work to about -5 c (25 f).
That is why home heat pump systems often use pipe embedded well below the frost line. Unfortunately that won't work too well for an RV.
Don't get me wrong--if my air conditioner ever flakes out--I'll replace it with a heat pump.
