This work investigates the performance of commercially available poly and mono Si photovoltaic (PV) modules under different temperature and illumination conditions. While mono Si module shows better solar cell features in terms of series resistance, reverse saturation current and fill factor, the photo generated current and output power of mono Si module are found to be much lower than those obtained with poly Si module. Lower photo-generated current in mono Si module is attributed to higher recombination in thick bulk layer of mono Si cell, which is probably due to the lower than required crystal grade of mono Si module. The findings of this work suggest the need for better regulation for quality control of commercially available PV modules.