Performance, quality and reliability issues are becoming more and more important for the emerging photovoltaic markets worldwide. The purpose of this paper is to present operational performance results of a PV system. The data analyzed here is derived from analytical monitoring data, hourly values, and 5-minute-values of a selected PV system installed in Tanta, Egypt. Results obtained by subjecting mono-crystalline silicon (mono-Si) modules to the assessment procedure are presented and discussed. Results obtained indicate that visual inspection revealed that the mono- crystalline module had cracked cells. This paper accentuates the importance of characterizing all module performance parameters in order to analyze observed degradation and failure modes. The analysis of the obtained results for real Isc after nearly 4 years of using show that Isc has been decreased by 9.7%, while Pmax decreased by 4.39%.