A numerical procedure for the extraction of the double-diode model parameters of photovoltaic (PV) modules is described. A particle swarm optimization algorithm is used to fit the calculated current-voltage characteristic of a PV module to the experimental one. As no recurrent solution was found in the large number of simulations carried out, mainly because of the stochastic nature of the optimization algorithm, statistics in combination with cluster analysis was employed to give an insight into the PV module parameters. This approach allows one to obtain a set of parameters which is reasonable and representative of the physical system. (C) 2009 Elsevier Ltd. All rights reserved.