I use these warmers on the lowest setting on 15gal plastic buckets. It keeps my goats water warm all winter long and we are in Maryland. One time I left the vevor belt on maximum and it did melt the plastic bucket but my fault. Lowest setting is about 80degree I believe and the water never freezes. Actually stays very warm. Saves me 10trips every morning. I have finally found something that works for me and my little heard of Nigerian dwarf goats. Definitely won’t be disappointed!