The PTC series of Day/Night Controllers by Custom Automated Products are perfect when you need to turn a device on only during daylight hours or only at night.
A photocell senses whether it is day or night, and turns the device plugged into it on or off depending on which model you are using. The PTC-1 turns on whatever is plugged into it during the day when the lights are on. The PTC-2 turns on the device during the night, when the lights are off. PTC controllers are rated for 15 amps @ 120 volts. 3 year warranty.