I think what we all need to realize is that chickens do not need heat in the sense that we humans do. Most breeds do just fine down to -20. I mean, think about it...like in my case, my coop is 5' x 8', I have 4 full-grown Black Australorp (they're big birds), lots of floor bedding. The body heat that they will produce in the dead of winter will keep the coop at around +30-35 which is perfect. Plus when you heat the coop on top of their own body heat there's always that chance that it will get "humid" in there, and that's something no one wants for their birds...JMHO