For some reason I keep thinking as other posters suggested a marine spec high charge rate alternator on the MH engine or a proper cold weather tech generator would be good backup when a week of overcast cold weather messes up the solar plans.
And a vented marine grade heater?
Our genuine Canada-spec Honda 5500watt generator ("Cold weather tech") starts with 2 easy pulls on a -35C day in the back of the truck when used to power a remote well pump. 5-30 synthetic oil and V-Power gasoline.
The trick to generators, Espars, Webasto's, engines, and pretty much any other equipment that uses fuel and lubricants is to use them from time to time so they run when you need them...