This paper presents a study, carried out with the help of the French Agency of Innovation (ANVAR). It deals with the conception of a small Savonius rotor (i.e. of low power) for local production of electricity. Our challenge was to design, develop and ultimately build a prototype of such a rotor, which was considered as a complete electromechanical system. An optimised configuration was chosen for the geometry of the present prototype. The building data were calculated on the basis of the nominal wind velocity V=10 m/s. Particular care was necessary to choose the appropriate generator, which was finally a rewound conventional car alternator. The whole design of the prototype has confirmed the high efficiency and the low technicality of the Savonius rotors for local production of electricity. The present prototype is to be tested in situ.