How much run time does it offer when fully charged?

The electrical parameters of this solar powered wall vent change depending on the sun's intensity. When the sun is most intense, the vent has a voltage of 18 and a power consumption of 26.5 W. In comparison, when the sun is least intense it has a voltage of 9 and a power consumption of 7.6 W. During the dark hours, the vent acts as a as an element of passive ventilation.