Energy consumption in developed as well as developing countries is high, especially in the residential and commercial building sectors. Researchers have been working on several technologies for the reduction of energy consumption in buildings; among them, energy-harvesting techniques are quite promising. In this paper, we explore a possibility of harnessing energy from grey water, while it flows down through high-raised buildings. We propose the usage of a micro/pico hydro turbine installed at the ground floor of a high rise building that utilizes the energy of grey water falling from floors above, to generate electricity. The electrical energy generated from the turbine can be utilized further in numerous ways. Scaled prototype of the same has been developed and tested. The proposed design of a gravity-energized wastewater system in high-rise buildings for generation of hydroelectricity is being checked for its feasibility in Indian markets. Calculation shows that the proposed system is commercially promising for most of the major cities in India. We also discuss cost benefits analysis of the proposed system to support our claims for possible commercialization of this technology. (C) 2014 Elsevier Ltd. All rights reserved.