My old coop has 1 window on 3 sides, 3 total, plenty of light in a 20 square foot coop.If you want to do right by your birds and save some electricity, set your timer to come on at about 2 or 3 am then go off after sun comes up. If a chicken (or anyone) doesn't get a certain minimal about of sleep it causes health problems and can cause fighting and insanity. Even in Canada, chickens don't need lights during daylight. It probably doesn't hurt them in daylight, but it cost you extra electricity.
I turn the light on at 5am and turn off around nine am. No lights after I lockup the coop,10 - 20 minutes after sunset. A 200 lumens LED uses 3 watts.
My new coop has two windows on one wall, it's dim even in brite sunlight. The coop is 22.5 square feet. I use a 200 lumens LED in there too. That's equivalent to a 25 watt incandescent bulb. I leave that one on till an hour before sunset.

A coop over 25 - 30 square feet will need a 550 lumens bulb a 40 watt equivalent incandescent, up to a 100 square foot coop. Larger buildings will need more of them 550 lumens bulbs evenly placed throughout or higher lumens. You should be able to read in all areas of the coop except the nest boxes. Hens prefer a darkened area to lay. GC