A combination of vertical axis wind turbine savonius and darrieus would have many advantages over an individual rotor savonius or darrieus. A savonius produces a high torque that would be useful in the automatic starter rotor and darrieus which has a high tip speed ratio useful for electric generation. However, research on combined rotors savonius and darrieus is very scarce. Although the peak speed ratio is still somewhat low for use as an electric generator, the research demonstrated a simple way to allow a darrieus VAWT to self-start and achieve greater efficiencies. Historically, VAWTs cost more to operate and maintain than HAWTs. Finally, traditional Darrieus rotors do not self-start under most wind conditions and the manufacture of their blades is a challenge because of the complex shape that adds expense to the turbine. However, evidence shows that a Darrieus turbine using symmetric fixed-geometry vanes can self-initiate in the field during atmospheric gusts, it was suggested that using a Darrieus blade together with a Savonius blade performs better than using them individually according to the turbine's self-efficiency capability. The use of a counter-rotating wind turbine with a free-rotation generator can produce greater amounts of energy than the common wind generators.