I found a pretty good solution for keeping the chicken water from freezing. I had bought a plastic heated pet bowl but then heard that it shouldn't be used for chickens. I'm not sure why but also it was a hassle to keep clean. I decided to keep a little water in it and place a pyrex bowl inside it that I swap swap out with a clean one each day. It has been working well even last Sunday morning when it was 12 below zero F. It only uses 35 watts. I'd like to find slightly larger glass or ceramic bowls but this works for now.