In a chicken coop, supplementing lighting has its pros and cons. Although it can lead to increased egg production by the hens, it's not the most natural approach to raising chickens. Before you add lighting to your chicken coop, take a number of factors into consideration.
If you choose to install artificial lighting in your chicken coop, be aware of the potential fire hazard and keep the bulb up and away from bedding. Never add a heat lamp to the chicken coop, as tempting as it may be to keep the birds warm.
How Sun Affects the Laying Cycle
Hens naturally lay eggs when the days are long and slow down as the days grow short in winter. Daylight stimulates the pituitary gland, which stimulates the hens' ovaries to produce eggs. Therefore, hens lay when they have light—sunlight or artificial light—for at least 12 to 14 hours per day.
Allowing Hens to Rest
Some chicken keepers believe that giving the hens a rest in the winter is important, choosing to deal with the lack of eggs during the shortest days of the year rather than using supplemental lighting. If you follow a sustainable, natural approach toward farming, you may decide that respecting the birds' natural laying cycles is important. However, if you are producing eggs commercially, this might not be a viable option for your business plan.
A Hybrid Approach
Rather than deciding on all or nothing when it comes to artificial light, there's a way to meet in the middle. Give the hens a natural rest in the fall as they go through molt and egg production drops and then stops. Then sometime after the winter solstice, set up the light and give them long days again. You may go a few months without eggs, but not the whole winter.
Adding Artificial Light
A 40-watt bulb suspended about 7 feet off the floor will provide enough light intensity to substitute for daylight in a small chicken coop of roughly 100 square feet (10 feet by 10 feet). For a larger coop of up to 200 square feet, use a 60-watt light bulb. You can set a timer on the artificial light to create at least 14 hours of light throughout the day.
When setting your timer, extend the day in the morning rather than the evening, if possible, because if the coop light suddenly shuts off and it's pitch black outside, the hens may become disoriented and not be able to find their roosts in the dark.
If it's already winter when you add the artificial light, don't suddenly flood the chicken coop with brightness for 14 hours a day. Add light for 45 extra minutes a week until you've reached the optimal amount of time to have the lights on. Additionally, don't keep the lights on around the clock. The hens need their beauty rest, too.
Raising Chickens for Eggs. UMN Extension