An analysis routine, based on electroluminescence (EL) imaging is presented for the quantitative determination of electrical performance parameters of individual crystalline silicon solar cells within a photovoltaic (PV) module. Specifically, the series resistance and dark saturation current density of individual solar cells are extracted, providing an in-depth diagnosis of PV module performance. The current-voltage (I-V) characteristics of the PV module can then be computed through solar cell one-diode modelling. By comparing the performance of the original module with that of a simulated module, where the solar cells with poor series resistance and dark saturation current density, are replaced by better cells, the potential performance improvement can be predicted. The technique is simple and enables a fast analysis.