I too use a heater in my coop. It is an oil filled radiating heater hanging in the middle of the coop, not designed for chickens, but works very safely. It sits on a concrete block and is suspended from the ceiling also to prevent tip overs. It is not intended to heat the whole coop, it can't and won't. It is intended to give them a place to come and warm up when needed. My temperatures don't go as cold as many of yours, but still I find my chickens on the low perches I placed around that heater on cold days. A few have chosen to sleep there on occasion. I do not have electricity in my coop, I run an 100 foot outdoor extension cord to the coop for the heater. I can reach right outside my front door and plug it in when temps drop to freezing and unplug just as easily when temps rise again. Our temps swing wildly so this was important to me. ( we had 11 degrees 4 days ago and its 60 degrees now) Cost of this heater is 50 dollars, longevity 3 years, have not noticed any jump in my electric bill so can't factor that in, but peace of mind is priceless. The way I see it, if I can offer something so inexpensive and safe to keep them more comfortable and free of frostbite, why wouldn't I? It's also a wonderful place to warm my freezing fingers when tending the chickens on those bitterly cold days. : )