Currently there are different methods to estimate the parameters necessary to model a PV cell or generator. The simplest ones are based on reducing the number of parameters, disregarding some of them or assigning an initial value. These methods use simple equations, often obtained empirically, and very easy calculations. Usually, the results are simple approximations, for which reason they must be considered unreliable. On the contrary, methods that give good results are often characterized by their complexity. Generally they need a large amount of data, which in some cases require statistical processing, in addition to equations and laborious calculations. The purpose of this paper is to present a low complexity calculation procedure that allows estimating the ideality factor and the loss resistances of any PV cell or generator. The proposed method is based on the five-parameter model and as input data it only requires the open circuit voltage, the short circuit current and the maximum power point voltage and current. The results obtained with it allow simulating any PV module of crystalline silicon with great accuracy. (C) 2011 Elsevier Ltd. All rights reserved.