It is relatively easy to make an emergency heat source for your snakes. As long as you don't have dozens of snakes in which case an emergency generator may be in order. At a hobbyist level and I'm only dealing with 3 snakes I have a cooler with a UTH, thermostat, and thermometer powered by a power pack with built in AC inverter. Put the UTH inside the cooler on the bottom, line the bottom of the cooler with water bottles filled with warm water, power the UTH with the inverter. Take advantage of your warm water while you have it. If you are on a well with a pressure tank, do the best you can until pressure depletes. Each snake goes into their own indivdual canvas bag. Drill a few ventilation holes. Heck any cooler would work. Don't know if I would use a Yeti. Kind of expensive drilling holes in it. A 12V DC power pack will power a 16 watt UTH for a very long time. As a bonus the power pack will even jump start your car.