One electric space heater keeps our rv warm/comfortable, even when it gets down into the 30's, and it is a lot quieter than the furnaces. If it is really cold outside, it gets down to about 50 inside, so I turn on the furnaces to give it a boost. If it goes down to the low 20s at night, then you need to turn on the furnace to keep the tanks and water lines from freezing. Outside, if it goes below freezing, you need to disconnect the water hose and stick it in a compartment or it will be frozen in the morning. Use the water tank and pump while disconnected.