In this article a procedure of electric power obtaining is presented, based on the micro-hydraulic application derived from the supply pressure of water in the cities; this constitute a step more toward the objective of sustainable buildings (energy and environmentally speaking), and is integrated into the generat electrical power management in biuldings with the main renewable energy systems for electrical supply (basicaly wind and solar energy). The proposed system can be more important in non-developed countries, where the electric supply is not totally reliable, and the water supply of the buildings is made by using water tanks on the top.