We weren't going to add light at first, we figured on just waiting to see if they stop laying. Well, it's dark when we leave for work and dark when we get home now, so I realized that I need to add light so we can see enough to change their water and refill their food. As long as I'm adding a light it might as well be on a timer and serve to maintain 14 hours of light for the chickens.
Their coop is only 4' x 6', and well insulated so I don't want to add heat, and I was a little concerned about the chance of fire with an incandescent bulb too. Last week I went to the hardware store and decided to get some LED rope lighting, like you see under some deck railings. It's very energy efficient, doesn't get hot, and weather proof. I was looking for a 6 ft strand, but they only had 18 ft lengths. I figured it would be brighter than necessary, but no big deal.
I hung the rope lights on cup hooks along the top of the walls around the inside perimeter of the coop. It's on a timer that comes on at 3am and shuts off at 7am.
Sunday morning was the first time using the lights, and DW asked if I planned to get up to make sure the lights came on as scheduled. I assured her I had no intentions of getting up at 3am. Well, in the middle of the night I woke up to a racket coming from the coop. I looked at the clock and sure enough it was 3:05am, so I went to the window to see what was going on. Every one of the chickens was out in the run pacing back and forth, squacking their heads off. The light was BEAMING out of the windows and vents. DW got up to see and said it was brighter than the Vegas strip.
They got used to it pretty quick, and haven't made any noise in the morning since.