We have a small generator that we got after last year's tornadoes, and thankfully we've never had to use it. I also keep instant hand warmers for emergencies, and for any small animals that I rescue.
My mom has to use a CPAP mask to sleep, so the only two things that really have to run are her mask and the snake's heating pad, though if it's for an extended period of time, I may have to use it to run some lights for my plants.