I told my husband that story when he wanted to put a light up in winter to keep the hens laying well. He came up with an awesome idea--he put up strings of Christmas lights! They are super-safe, and easy to string up wherever you need them. They don't heat, of course, but we didn't need that, as our coop is just big enough for the number of hens we have, and they are able to keep it pretty cozy with their own body heat.
What a cute idea! I need to figure out if ours will need heat during the winter or not. If they don't, that is a cute idea.