A simulation of shading effects in arrays with different string configurations has been done. Simulation has been performed using as the basic unit the solar cell, modelled in direct bias by the conventional one exponential model, and in reverse bias by an equation previously validated in different types of photovoltaic cells reverse characteristics. The influence of the amount of shading, the type of reverse characteristic of the cell, the string length and the number of shaded cells has been analysed, and some recommendations are extracted. (c) 2005 Elsevier Ltd. All rights reserved.