Dusk to dawn porch lights are exterior light fixtures that are specially designed to turn on at dusk and turn off at dawn. By following this schedule, these lights provide lighting during the night but save energy by being off during the day.
Dusk to dawn porch lights are usually activated by a photocell, which is a device that senses light. The dusk to dawn light will turn on when the photocell does not detect sufficient natural light. When the photocell detects light, it will turn the fixture off. This design allows the lamp to provide lighting only when it is needed to illuminate the surrounding area.
Dusk to dawn light fixtures are also sometimes used as a piece of security equipment to deter potential criminals from using the darkness to hide themselves.