It would probably need to get 10 degrees below freezing before overnight cooling could become a threat. Establish your own relative risk when it is 30° or 25° without the furnace running -- put a thermometer on the floor in your Airstream -- check it first thing in the morning. Should be easy to get in there early enough with the @(*&)%($&*@# daylight savings time keeping it dark until 7:00AM. (I thinking of joining the 'OccupyGreenwich' demonstrations until they give us our nights back... Did I say that? Okay, won't go there.)
Originally Posted by Kosm1o
You need to run the furnace to keep water under the floor from freezing. Running an electric heater will keep the furnace from coming on.
Bingo! Furnace is your best choice. The overhead A/C won't get down to the floor & under the cabinets as well. Heat rises, etc. And does your A/C have a heat strip? Or does it have a heat pump? These are different. There would be some concern about a heat pump needing more than the 15 amps that a 3-pronged house outlet could provide. The potential downside is wear and tear on the compressor. A different discussion... But this would be relatively ineffective in any event and you aren't going to be using much propane. Or so what if you use a 30# tank anyway? ($22-24 around here)
Here's what I would do. Your pipes are secure if you run the furnace -- say on about a 50° setting. This won't use much fuel. The only winterizing necessary for the fresh, gray & black tanks is drain them -- they don't get the pink antifreeze treatment anyway. You're set. Enjoy your norteņo winter!