The present research is concerned with the experimental determination of the efficiencies and performance simulation of Darrieus vertical-axis wind turbines. The tests were performed using reduced models in a wind tunnel. A new method for obtaining the turbine power was developed. The classical approach would require large models and a huge wind tunnel to facilitate the torque measurement. Once the characteristic curves of reduced models were determined, in a dimensionless form, a performance simulation of real size turbines was developed. Such a simulation involved two Brazilian regions (Fortaleza and Fernando de Noronha) and the knowledge of the hourly wind distribution.