This paper presents a validation study on series resistance determination of photovoltaic modules on the basis of the IEC 60891 edition 2.0 (2009) normative standard. A selection of different technologies has been investigated, ranging from polycrystalline silicon to thin film modules. Their I–V characteristics have been measured at the European Solar Test Installation under various operating conditions with respect to module temperature and irradiance. The aim of this research work is twofold: firstly, it contributes to the quantitative assessment of the effect of the various calculation parameters on the overall precision of the series resistance; secondly, it provides information about the dependence of series resistance on module performance over a wide range of irradiance and module temperature. A comparison with the previous calculation procedure from the first edition of the IEC 60891 (1987) has also been performed in order to understand how the differences between the two methods can affect the final results. Copyright © 2011 John Wiley & Sons, Ltd.