Is this a hobby or a commercial operation? If commercial, the literature exists and should be widely available from your local extension service, and most people who are buying eggs in winter will have to select from eggs which are laid in winter (making the nutritional concern moot).

Hobbyists tend to do things like name their chickens, not light and keep animals after they have passed their productive age. Commercial operations often have humane processes but with metrics and flows that "pencil out" and involve lights, distinct cadres/cohorts of pullets and culling older birds.

I used light the first year but did not see a huge increase in production for the cost of feed and the additional electricity. I decided to let my girls lay according to their natural seasonal cycle and just be hens (and friends).
This is the first year I do not have a rooster and the girls seem much calmer also, though I do miss the crowing at all hours of the day and night!

Michele

Hi Kasia, I have a red heat lamp (the kind used in bathroom fixtures to heat from above) hanging in my coop for my girls all winter long. It is plugged into a timer and comes on around 6 pm now that it's darker earlier and they roost about that time, and it goes off around 8 am. I figure the red light is a lot less disruptive to their cycles that a bright light bulb on all night, and based on the fact that they have plenty of room to roost all sorts of places, and they are ALWAYS right near it at night, that tells me they like it. People in cold climates say their chickens live through the winter without any heat at all, and I believe they do, but how comfortably??? I want my friends to be as happy as possible and they choose to sleep near the heat lamp. I'm also in the expensive organic feed camp, and really it all seems to go together if you ask me...