A method for the determination of a control reserve of one or plural wind energy plants, for the operation of which a desired value for at least one electric variable is preset, and for which a control unit is provided which has a power curve, which contains a maximum value of the electric variable depending on values of the wind, the method having the following steps: the control unit determines a maximum value of the electric variable from the actual value of the wind and subtracts a current value of the electric variable from the same, the control unit transmits the determined maximum value and/or the difference as a control reserve to a higher order control unit and/or an external utility.