The girls don't lay in the winter. It's part of their natural cycle, and we don't provide them with a light bulb. Often done for a little additional heat in cold weather, the bulb encourages them to lay, too. (It's the length of day that gets them to start and stop.) We decided we didn't want an extension cord running out to the coop, and we also thought if Mother Nature thought they should just focus energy on eating and surviving it was good enough for us.
Our flock is small and so is their coop. The roof opens up so we can lean in to do a count at night, collect eggs, and tidy things up. They have a bar to roost on, and two nesting boxes. We cleaned out the coop in the fall and put down a thick layer of cedar chips. As the girls make their "deposits" we add more cedar chips. The heat created by the composting process helped keep them warm, and will make some excellent fertilizer for the garden, too.
A small door on one end lets them come and go during the day, but we close them up at night. This is sometimes the hardest part, especially if we're out of town. We close them up after they go to bed (or we entice them to bed early if we're going out for an evening) to protect them against predators. Raccoons and opossums are waking up looking for that first post-hibernation snack, and I have no doubt the coyotes know about our little poultry buffet, too. We sleep better knowing they sleep safely.