The Wayne model WSS30V is a combination primary sump pump and battery backup sump pump. The primary pump will operate on 120 volts and the battery backup pump operates on 12 volts from the battery that is installed along with the system and will operate when there is a loss of power. The battery backup pump will also operate in the event the primary pump cannot handle the incoming water, but will operate using the battery power and NOT 120 volts.