Dependong on the size of your coop, mine is sized to keep only a few birds in there, I have 4 standard and 2 bantys now, and I only use a light as a heat source on VERY cold nights and they seem to do fine, I do have the run covered with plastic with a couple gaps to let in some fresh air but keep out the wind. Last year I had the lights on (I built in fixtures that I turn off by unscrewing the bulbs) for about a week 24 hours a day, some say that is too much light, but the did fine, then when the weather warmed up I used a timer and a clip on light that I secured with a wire so that they could not knock it down and cause a fire hazard. Chickens are surprisingly hardy and will do well with just a little warmth.