I was wandering about the same thing. Add to that, the heating system. Cheaper to run the propane furnace, or use an electric space heater (supplemented with the furnace, to keep the water lines from freezing)? I'll be spending next winter in Texas with metered electricity.
2013 Eagle 266RKS
2011 Ford F-150 w/3.5L Ecoboost & H.D. Tow Package