In the emerging photo-voltaic markets worldwide the use of appropriate estimation of the operating performance of the grid-connected PV systems is becoming more and more crucial. The widely used performance indices that are used to analyze the system performance with respect to energy output, solar resource and the effect of system losses in its various components are total yield, final yield/specific yield, performance ratio, PVUSA rating, and performance indicator based on ratio of ac power at PTC to dc power at STC. This paper presents performance analysis of a 43 kW amorphous-silicon thin-film grid-connected PV system. Recorded plant monitoring data during July 2011 to July 2014 is used for the analysis. Major operation and maintenance issues encountered in last three years are also reported. © 2014 IEEE.