Originally Posted by DXSMac
I second the oil filled heater. If you are plugged into a 20 amp, (and not using ANY OTHER APPLIANCES ON ELECTRIC) use a 1500 watt for main part of RV (pulls 12.5 amps) and use a small 400-500 watt oil filled (3-4 amps) in the bathroom. The small one in the bathroom will keep the bathroom toasty. Put the frig on propane if you have to.
I agree with the lady. If you are plugged in just use electric heaters. Even though one 1500 watt and one smaller one are all you can use with 20 amps service, that will be enough to keep it reasonably warm.
The original poster did not mention whether or not the RV is winterized. Electric space heaters won't keep the tanks and plumbing under the floor warm but the LP furnace will. If there's a risk of your storage unit going well below freezing you need to consider that.
If you have a slide, keep it retracted. It seals better when retracted.
Of course, when you return to the RV, if there's no problem with CO in the storage unit for a short time, start the LP furnace to warm the coach quickly.