This paper presents the experimental results of the vertical axis wind turbine (VAWT), especially the Savonius rotors, which are developed for application on top of buildings due to lower wind speed compared with remote areas. The VAWT is regarded as the most suitable elegant candidate to be integrated with buildings for its relatively low operating noise, easy maintenance, and easy access. This study explored the interaction effect of the overlap ratio, phase-shift, and stage on the performance of the Savonius rotors in details. The results show that appropriate choice of the phase-shift angle according to the overlap ratio can not only increase the power coefficient of the Savonius rotors but also eliminate the negative static torque and smooth the variation of the static torque coefficient. Moreover, the performance of the two-stage rotors indicates that the two-stage rotor is the best candidate for this type of wind turbines or as a starting assistant for the Darrieus rotors.