In the paper, results of electrical modeling of Cu(In(x)Ga(1-x))Se(2) (CIGS) thin-film photovoltaic (PV) modules are presented. Whether the equivalent double diode model-DEM (Double diode Equivalent Model) is appropriate to model CIGS PV modules was investigated. Modeling was based on large amount of data (including current-voltage (I-V) curves) collected during long-term outdoor monitoring of PV systems. The process of applying baseline physical parameters to two of five DEM parameters: diffusion I(S1), and recombination I(S2) related components of dark diode saturation current was carried out. Modeled I(S1) and I(S2) values were used to replace previously approximated DEM parameters and then to predict measured I-V curves in order to determine electrical parameters of the PV modules. The parameters are used to predict energy yield in natural operating conditions. Results of modeling are presented and compared with measured data. (C) 2011 Elsevier B.V. All rights reserved.