In this study, the exergetic performance of a flat plate solar collector (FPSC) setup with ZnO-based ethylene glycol (EG)/water nanofluid as a working fluid has been evaluated against that of EG/water. As a passive means to augment the rate of heat transfer, internally grooved tubes of two different pitches (e=0.43 and e=0.44) have been examined and compared against the performance of plain tube. The mass flow rate was fixed at 0.015 kg/s and the volume fraction of ZnO nanoparticles is φ = 0.02% v/v. The results indicate an enhancement in exergy efficiency of 44.61% when using the grooved tube (e=0.44) against plain tube without the nanofluid and 39.17% when nanofluid is used. Using the nanofluid enhanced the exergy efficiency of the FPSC by a maximum of 73.81%. Maximum exergy efficiency obtained was 5.95% for grooved tube (e=0.44) with nanofluid as working fluid and is in good agreement with previous literature. Exergy destruction/irreversibility due to temperature differences and heat flow within the system has been reported. Sun-collector temperature difference accounts for nearly 86-94% of the irreversibility. The results for thermal efficiency of this experimental setup have been published and summarized in this study for reference. © 2018 by ASME.