Miscanthus × giganteus is a perennial grass that is considered to have a high feedstock potential for bioenergy production. Assessment of that potential is however highly related to the crop yields and to their change through the crop lifetime, which is expected to be longer than 20 years. M. giganteus is known to have an establishment phase during which annual yields increased as a function of crop age, followed by a ceiling phase, the duration of which is unknown. We built a database including 16 European long-term experiments (i) to describe the yield evolution during the establishment and the ceiling phases and (ii) to determine whether M. giganteus ceiling phase is followed by a decline phase where yields decrease across years. Data were analyzed through comparisons between a set of statistical growth models. The model that best fitted the experimental data included a decline phase. The decline intensity and the value of several other model parameters, such as the maximum yield reached during the ceiling phase or the duration of the establishment phase, were highly variable. The highest maximum yields were obtained in the experiments located in the southern part of the studied area and the duration of the establishment phase was strongly related to the establishment method. Since energetic viability and profitability of M. giganteus hinge critically on yields, these results could be integrated in further assessment works.