Ok, I can accept those figures (I never believed the smallest unit would ever be adequate; I just wanted to see if you could actually back it up with something more solid than your opinions); there are a few points, though:
The largest unit draws only 22A (at 240v).
Propane furnaces normally cycle on and off. Cheap Heat can run full time so it usually can put out the same amount of heat as a lager rated gas furnace. Of course, we don't know if that furnace ran full time or not during the night. We also don't know the ambient temperatures.
Aqain, all one would need would be a two stage thermostat (and, if the thermostat leaves the first stage on when it switches to the second stage, a relay) to allow the furnace to switch from electric to propane when and if the temperature drops too low for the Cheap Heat to keep up with.
I stand corrected on the location.
While I'm at it, Trailer Life recently had an article on the Cheap Heat. You all can read it
here.