
"Plug it into a standard electrical outlet, and its thermostat automatically turns power on if the air temperature falls below 35°F. Automatically shuts power off when temperature rises above 45°F."
A $13 thermocube (Google to find one) can be used along with a $15 dog electric water dish from Home Depot during the winter. Even if your coop doesn't have electricity, you can safely run an adequate-grade extension cord to use the thermocube and a low watt light bulb.