Energy consumption in buildings has been an important share for the global energy demands. Building nearly accounts for 40% of total global energy consumption hence one of the biggest consumers of electricity. This paper aims to harvest the potential of rainwater potential energy to power the buildings during rainy season hence provide them with a clean renewable source of energy so that we could solve two major world’s issue that is Energy and Pollution. A sample model of the building was studied and then calculations were carried out using the fundamental principle of fluid mechanics and turbomachinery. Keywords: Buildings, Hydro-Power Plant, Rainwater, renewable energy, turbine, Potential energy. Introduction In context to the present scenario of energy demand rising all over the world especially in developing countries, new and best ideas are coming regularly. One of the ideas is of Hydro Power Plant which is an extension of rainwater harvesting, in which along with the harvesting of rainwater we can also produce electricity through the rain water without polluting or leaving any adverse or side effects to the environment as well as the ecological and sociological system. This green energy idea can provide about 90 kW of energy which can fulfil the energy needs of about 150 families of about 5 members in a family. Since the major part of the energy is consumed by the high rising buildings so we made an effort to fulfil the energy