This may sound silly, and I have not tried it, therefore I cannot recommend it.
However, if you are shy on electric lines going to the coop (for whatever reasons: lack of funds, fear of fires, etc..)
I met a gentleman in the hunting isle (not me, the Rev. was) he had a cart full of those keep warm packages...(cna't think of the name sorry) you simply squish them and they put out heat to keep hands or feet warm while outside, they work for up to 8 hours.
We talked about hunting, and he said, quote "I put these up under my waterers...it keeps the water from freezing on cold nights"
So there, absolutely no tried & true personal testimony, but thought I would pass it along.
However, if you are shy on electric lines going to the coop (for whatever reasons: lack of funds, fear of fires, etc..)
I met a gentleman in the hunting isle (not me, the Rev. was) he had a cart full of those keep warm packages...(cna't think of the name sorry) you simply squish them and they put out heat to keep hands or feet warm while outside, they work for up to 8 hours.
We talked about hunting, and he said, quote "I put these up under my waterers...it keeps the water from freezing on cold nights"
So there, absolutely no tried & true personal testimony, but thought I would pass it along.