When it gets cold, your first reaction may be to fire up the gas furnace. That works, but here are some other suggestions:
Use a portable indoor propane Heater (Mr Heater Buddy)
These portable propane heaters are rated for indoor use and put out enough heat to keep your RV living space warm. A single $2 propane canister can heat your RV for up to 6 hours. They can also be connected directly to a large propane tank.
Mr Heater Portable Propane Heater - Indoor Safe
This is a great little portable heater that can run off of small propane canisters (1 = 6 hours) or be connected to a large propane tank. IT s a great remote camping accessory when you don't want to fire up your RV furnace.
DC Powered Electric Blanket
This small electric blanket is perhaps my favorite boondocking accessory. It can be connected to a DC power receptacle and provides enough temporary heat to warm you up. I simply put in my bed and fire it up 10 minutes before climbing under the covers. Toasty! If I get cold in the night, I hit the button to warm it up for another 45 minutes then it automatically shuts off to conserve power. It only draws about 4 amps while running.
12-Volt Polar Fleece Heated Travel Blanket
This is a small blanket (not full size) that I use frequently to keep my bed warm. It doesn't use a lot of power and just runs for 20, 30 or 45 minutes based on what you choose on the control. Trust me it's enough to warm keep warm. If you get cold again, simply press the button again. It's powered by a 12 volt receptacle I installed next to my bed and works great.
Move to Warmer Climates
Finally, if cold just isn't your thing, simply do what most full-time RV owners do. Pack up and drive south until the climate suits you.