The Sun-Mar Centrex 3000 is an extra-high capacity unit designed for very heavy cottage use or heavy residential use. The Centrex 3000 is an electric unit for those with a constant electric supply. All Sun-Mar composting toilets incorporate a patented Bio-drum which ensures fast and odorless decomposition. Saves thousands of gallons of water, while recycling waste into soil. The unit is shipped fully assembled. A one pint flush toilet is required for use with this unit (sold separately). Seasonal capacity: 9 adults or families of 11. Residential use: 6 adults or families of 8. Other optional configurations available for this system include: 1) Waterless operation: This configuration requires the separate purchase of the Sun-Mar Dry toilet and the Sun-Mar A/F Waterless kit 2) Dual electric and non-electric operation: This configuration requires the separate purchase of the Sun-Mar AC/DC kit.