In this communication, an attempt has been made to investigate the performance assessment of a solar photovoltaic (PV) array system based on electrical energy output and power conversion efficiency. Simplified mathematical expressions for evaluating performance indices using experimental observations for entire PV array and its individual component subarrays on daily, monthly and annual basis have also been developed. Experiments have been carried out on two individual 1.2 kW(p) and 1.12 kW(p) component subarrays of 2.32 kW(p) stand-alone PV array system for climatic condition of New Delhi (latitude: 28 degrees 35'N, longitude: 77 degrees 12'E and an altitude of 216 m above mean sea level). Individual performances of both component subarrays were evaluated and its effect on the actual performance of entire PV array has been presented. Numerical computation was carried out for a typical clear day in the month of July 2010. It was found from experimental results that daily power conversion efficiency of entire PV array and its component subarrays1 and 2 were 6.24%, 9.5% and 3.9% respectively. For more effective performance assessment of PV array/subarrays, on field experimental performance results have been compared with the rated (max.) results estimated at STC and also with the maximum performance results estimated for actual climatic conditions as obtained during experimentation. (C) 2011 Elsevier Ltd. All rights reserved.