No, as they are solar powered they only operate during the hours of daylight.
The Solar Star attic fan features a brushless DC motor that reduces noise and lightweight, polymeric fan blades that minimize vibration. The result is a whisper-quiet operation.
The Solar Star attic fan runs best when the solar panel is in direct sunlight. Although the unit will continue to operate in the shade (provided the sky is bright), however it will run at a reduced speed.
Attics are meant to be ventilated year-round, and the Solar Star attic fan is designed to run whenever daylight strikes the solar panel. During the winter, proper ventilation helps prevent condensation from forming within the attic. If moisture does accumulate, it could cause significant heat loss from the home if the attic insulation gets wet. A cool, dry attic is the best solution for keeping heat inside during the winter. If your attic is properly insulated and moisture buildup is not a concern, but cold temperatures are, then the optional Solar Star Thermal Switch may be the solution for you.
Whilst the Solar Star Attic Fan does not have an on/off switch, the optional Solar Star Thermal Switch can be added to turn off the fan when the temperature in the attic is cooler than 18° C. It will also turn on the fan when the temperature in the attic is warmer than 29° C, giving you greater control over the operation of your Solar Star Attic Fan.