Some electric blankets work fine.  A 45Km reel of 8AWG is the problem.

Pity solar doesn't work at night.

Top down, waterheater mylar bubblepack on the windows.  Use the Coleman
Catalytic until bedtime and again in the morning.  No need for a heater
whilst you sleep.  You're asleep.

650CI fill down bag works well.  Wear a hat or a squirrel coat with say 11
squirrels.  Put a ferret in your trow.  A 60s era winnebago I encountered
while searching for enlightenment regarding native trout had a Jotul stove
mounted on the floor.  Warm and toasty.  Still takes O2 to run it though but
in that leaky winnie that wasn't an issue.

One candle will keep things a bit warmer.

Hang the modesty panel in the front and make sure it's really close to the
window surface to eliminate as much condensation as possible.

Rise early, fetch the ferret.

pensioner (uses an electric blankie when on shore power)