I actually keep my rat racks in with my racks of ball pythons in a small 10' x 20' room. The heat of the rodents keeps the room pretty warm when I turn off the heater and clean things up, it cools off a few degrees but since I have hundreds of rats in there I wouldn't think it would get too cold if the power went out long term. Who would have thought that you can heat a house with rats LOLOLOL.