Producing power through renewable energy systems in buildings, known as green buildings, is becoming more and more crucial and also popular in these days. In this paper we are introducing a new system by which it is possible to produce more than 1000 watts electrical power. The system works by wastewater generated from domestic activities such as laundry, dishwashing and bathing, known as greywater. To this end, it is necessary to have a vertical sewage plumbing system which is located inside or outside of the building. Conducting greywater of each floor to the plumbing system, it is possible to use plumbing system height and greywater pressure if we dam the end of the plumbing system. Whenever the pipeline fills completely with greywater, the fluid has constant pressure and makes sufficient turbine head that can propel the propeller of a turbine. This Waste to Energy (WtE) system is capable to provide notable electrical power of needful light or other public electrical facilities of a typical building complex. The turbine can produce electrical energy according to the height of the building (sewage plumbing) and its habitancy. The higher and more habitant the building, the more energy is produced.