The analysis of the degradation of tandem Micromorph thin-film photovoltaic (TFPV) modules and its impact on the output power of a PV array under outdoor long term exposure located in Jaen (Spain) is addressed in this work. Furthermore, the evolution of main solar cell model parameters is evaluated by means of parameters extraction techniques from monitored data of the PV system in real operation of work. The degradation rate and the stabilization period of micromorph TFPV modules are evaluated. The analysis of the degradation rate, together to results obtained for the evolution of each of the solar cell model parameters along the outdoor long-term exposure allow a better understanding of changes in performance of micromorph TFPV modules and the behavior of the output power of the PV generator. (C) 2016 Elsevier Ltd. All rights reserved.