A quartz halogen light is very bright and lasts a long time. The amount and type of light in a barn affects the safety and efficiency of everything you do, from feeding to grooming to cleaning stalls to just walking through. Lighting is provided by a combination of natural and electric light sources. Translucent fiberglass panels are less expensive, and generally easier to install. These panels work well on walls also, but must be installed only where a horse can't reach them.
Windows provide ventilation as well as light.
Protect them from damage and your horse from injury by installing sturdy steel bars or heavy screen over them. It works by heating tiny tungsten wire filaments with electricity. The glass bulb provides a vacuum which delays the filament from oxidizing. And they burn out quickly, lasting only 500 to 1000 hours, or 20 to 40 days of continuous light. On the plus side, incandescent bulbs are cheap and easy to replace.