System for evaluating and controlling the efficiency of a wind turbine

The invention relates to a system for evaluating the efficiency of a wind turbine (3), with a control system comprising means (11, 15) which are used to measure meteorological parameters M1, M2 and are respectively arranged in the wind turbine (3) and in a meteorological tower (5), and means (13) for measuring the orientation beta of the wind turbine and the power Pr generated by same. The system according to the invention comprises a computerised unit (21) which is connected to said measuring means (11, 13, 15) and provided with a first calculating module (23) designed to obtain a characteristic power Pc as a function of said parameters from the data obtained during a first operating step, and a second calculating module (25) designed to obtain the mean deviation Dm between the power Pr actually generated and the characteristic power Pc according to the function obtained by the first calculating means (23) in the set of at least one series of data.