I think the answer is:
A 110V 1500w heater is 5000btu and are all rated close to the same ON HIGH SETTING.
The little Atwood propane furnace is closer to 16,000btu and some of us have 30,000 btu furnaces.
My 4k generator gets, if I remember correctly, 100mpg when running.
My propane seems to get even better when running the furnace.
Its not an exact mileage, it's a counter to a worrisome but kinda nonsensical due to smallness, mpg argument.
If the cost differential is anything other than merely interesting, don't take the trip.
(and I haven't found a 110v space heater that wouldn't tip over during even a slightly harsh brake tap. You'd have to screw it to something non flammable and solid in order to keep it upright)
https://www.amazon.com/Bestauto-Muff...7032929&sr=8-7
And I'm pretty sure I really like these. I've done a lot of research and can't find a reason to not install one. I'll put the diesel tank right next to the generator, using the generator hatch as a way to fill it. It'll make a nice 100% independent(with its own battery) source of heat. No dependence on anything other than itself. It's been difficult for me to find run times, but I've deduced a pint an hour(8hours a gallon).
And
https://www.amazon.com/Output-Auxili...7033177&sr=8-2
I already have one of these that'll maybe be spliced into the v10 heater circuit. I'm undecided. It's on the mod bench being stared at.... It's an easy mod, it's there, it's a nice fit. My v10 uses 6/10ths of a gallon an hour when idling...this is vaguely similar to the $12,000 AquaHot option on big class A coaches.