The Centrex 1000 AC/DC is a hybrid power unit meant for light seasonal applications where the availability of AC power is uncertain. Employing a dual vent stack, the 1000 AC/DC is vented passively in the event of a power outage, or can be used solely on a non-electric basis until 110v power is put in. You can choose to hook up both or just one of the vents, depending on your power situation. All central units, including the Centrex 1000 series, are fitted with a removable evaporating tray under the drum screen in the evaporating chamber. This tray helps to trap any peat moss debris, and provides an extra evaporating surface. In light to medium seasonal use the Centrex 1000 AC/DC is typically able to hold compost for the full season, and compost needs extraction only in the Spring. The Centrex 1000 AC/DC features a 250 watt heater in a sealed compartment under the unit and the standard Sun-Mar 30 watt turbo fan and 2" vent stack to ensure odorless operation. It also features a 4" vent stack which is meant to passively vent the unit when non-electric operation is required. This unit is ideal for those who do not have power now but are expecting it in the future, or for those who have generators that can only run part-time. All Centrex 1000 series units are supplied with a 1" drain hose which should be connected to the 1" drain at the bottom left of the unit. Click here for more information about handling excess liquid. The Centrex 1000 series is designed only for use with 1 pint flush toilets (purchased separately).