I moved mine out to the coop at 2 weeks, we had 26 and they were really getting over-crowded for the brooder, our coup is 10'x12' so we took one side where the roosts are and cliped on the red heat lights, It was pretty warm when I moved them out there and one 250 wt bulb was enough, then it turned cold, down to freezing and went up to 3 of the lights, haven't gotten the electric bill yet but with 3 250wt bulbs going almost 24/7 I'm sure it will increase, but the babies, now almost 4 weeks old they are very happy to have all that room, and love the sun coming in during the day. I just have to monitor the temp accordingly.