Provided is a method of determining a power curve, which specifies a correlation between wind speed and a power output of a first turbine. Wind speed is calculated based on a measurement correlation, specifies a correlation between the rotor behavior and the wind speed, derived from rotor behavior. The measurement correlation is trained using a second turbine of identical construction having a sensor. While the second turbine is operated at varying wind speeds, the sensor repeatedly records and assigns a wind speed to a simultaneously recorded rotor behavior of the second turbine to produce the measurement correlation. The power curve is produced by repeatedly and simultaneously recording a power output of the first turbine and an associated wind speed while operating the first turbine at varying wind speeds. The wind speed is calculated from rotor behavior of the first turbine based on the measurement correlation trained using the second turbine.