Very good info here I see, I have the doulbe payne glass, good insulation and have spent a 6 day period where temps did not get a bove 18f, no problems. Presently I have LP for cook top and refrig, however am scheduled Jan 7th to change to a house type refrig, all elecric coach, where the LP tank is, will then be home for 2 more 8D Gel batteries, bring total to 5 8D Batts. That hould hold for a while I hope.
For me, one of the nice parts about the A-H heat system, not only the living area staying comfy, but with the basement thermostat, can dial in what you like there too, I set it at 40f, then you also have the ability of preheating the Cummins ISM500 in addition to the elecric block heater, so a cold start is little concern so far. Fuel capacity is 194 gal diesel.
Presently Vero Beach, Fl on way to Arcadia Fl for a bussin event.