Solar lights use a solar panel to convert sunlight into electricity. Solar lights are a good choice for a lighting system where wiring isn't possible. During the day, the rechargeable NiCad batteries are charged for use at night. Most solar lights can run for three years before you need to replace the batteries. Solar lights are usually used as accent lights because they are dimmer than standard low-voltage lights. You can test the lights by covering the photo eye sensor on top of the light.