With the new solar system installed, electric heating is now possible. Now, there's no guarantee that a bar heater is going to help much but the reviews are good and it's designed for greenhouses. I like to think my insulated space is a touch warmer than a greenhouse to begin with, so I'm expecting results...

This one takes 80 watts, which my battery and inverter can easily handle. Higher rated heaters are fine, but I don't want to kill my battery and this is an experimental device as far as I'm concerned. The hope is that it will slowly warm the space and keep it livable without getting hot enough to pose a fire risk. That way, it can stay on overnight and I can avoid losing toes to frostbite over the winter.