I might add another counter-intuitive two-cents worth on electric heaters for use in an RV.
IMHO, 1500 watt electric heaters don't all output the "same kind of heat". We tried both a hot-air 1500 watt heater and a radiant 1500 watt electric heater in our motorhome during the fall months last year ... living in it almost full-time while the stick house was being remodeled.
Of the two types of electric heaters we tried - the radiant heat type was far superior in making us feel comfortable immediately and continuously. The radiant heater was physically much larger, but if we were to do serious cold weather camping and mix some electric heat in with propane furance heat ... I'd definitely want the electric heat watts to be of the radiant type.
It seemed to us like we were getting way more comfort per watt with the radiant heater.