My dad gave me a "Thermocube" brand plug in. The really cool thing about this plug-in is that it automatically turns on the plugged-in heat source when it senses 34 degrees Farenheit. It costs around $8 the last I checked at my farm and garden store. The Thermocube looks like a 3-way splitter for a standard outlet plug and is about the same size. It plugs into a standard electrical outlet. I love mine (and so do my chickens) as our weather is constantly unpredictable here in the great northwest. The evening can be mild and dip to a heavy frost by the next morning. Conversely, an evening can be cold and then turn mild by morning. I'm cheap so I hate wasting energy heating a coop that doesn't need it and I want my hens to be comfortable and have something to ward off the damp. We get an average of 120 inches of rain a year. (Yep, 10 feet of rain annually and sometimes more!) so dampness is a huge issue. Be careful about having things near the heat source that can catch fire. Also be careful not to overload circuits with too much plugged in. I have my 75 watt heat lamp suspended by lightweight chain about 30 inches off the floor in the center of my coop. During the few frigid days/night we get the chickens get off their roosting sticks at night and huddle underneath the lamp. None of the chicken folks/pet lovers locally knew about this cool resource so I thought I'd share my limited knowlege with my fellow chicken-lovers! Happy winter!