The purpose of this project is to evaluate the feasibility of a water treatment plant at a given location, supplied partially or entirely with renewable energy. The system analysed is a PV/Wind hybrid system. Economic and technical conditions for the system are calculated. The power demand of the plant, determined by the water demand at the given location, will be met by renewable energy to a degree depending on local weather conditions and the technical products used. This will result in a yearly coverage ratio of renewable energy, which determines the power need from the distribution grid as well as the payback time of the system. A case study is made on an existing water treatment plant at Fårö. The result shows that the cover ratio, with power supply from sun and wind, would reach 62 %. However, the total energy produced by the hybrid system exceeds the demand. In order to use all the energy produced, the hybrid system would need energy storage and a possibility to sell excess energy to the power distribution grid. A sensitivity analysis of the hybrid system is made by changing ingoing parameters and components.