This paper experimentally investigates the exergy of a riser tube with heat transfer enhancer in the flat plate collector. Two different internal heat transfer enhancers are used herein, namely, rod heat transfer enhancer and tube heat transfer enhancer. The environmental and sustainable assessment of the flat plate collector with and without heat transfer enhancer have been taken into consideration in the study. This is the first study performed on the exergy and economic analysis of a flat plate solar collector using this heat transfer enhancer, and the new findings on the exergy analysis using heat transfer enhancer of the flat plate collector have been reported. The improved exergy efficiency, useful exergy rate and exergy destruction for the flat plate collector are analyzed, and it is found that the rod heat transfer enhancer provides comparatively higher exergy efficiency than the tube heat transfer enhancer and plain tube flat plate collector. The maximum exergy efficiency is 11.3%, 10.9% and 8.3% for the rod, tube heat transfer enhancers, and plain tube respectively. The heat transfer enhanced collectors significantly reduce the total exergy destruction compared to plain tube collector. The increase in useful exergy rate is 1.29 and 1.25 times higher for the rod and tube heat transfer enhancers respectively, compared to the plain tube collector. The conclusion is that the rod heat transfer enhancer collector has the lowest energy payback time and a simple payback period. © 2017 Elsevier Ltd