Size of Generator needed

[Coug]

It has a vent fan like for a stove in it. And I have four 1.something amp hour batteries and 2 250 watt solar panels and that is the plan to put the panels on the roof.

Since it has the 24V slave cable, there might already be some things inside designed for 24V like some lights or the fan or whatnot. If that's the case you're pretty much good to go already. If not you might look at just getting a decent inverter to power the lights and stuff instead. With that much panel output you should be just fine for whatever you want to do if you're smart about it.
just have to verify what the diesel heater voltage is supposed to be (if it's a powered one) and you'll be good for all but summer.

Can always make some sort of secondary roof over it to keep the sun off everything but the panels to keep the temp down in summer as well. (I was thinking canvas tarp or something, but depending on how much height you have to play with above it could just do a hard roof with a 4 inch gap to mount the panels and provide shade)

 

[staker]

I made a mistake only have 2 batteries but should still be enough. I would like to make a cover for the panels out of aluminum that could open up. so that could be the second roof. I guess then all I have to do is find the right size of an inverter. Thanks for the help.