In this study, a photovoltaic thermal collector)PVT(has been constructed in Karabuk University, Turkey to investigate the effects of utilizing multiwalled carbon nanotubes (MWCNT) and graphene nanoplatelets dispersed in water as a base fluid with a concentration of 0.5 wt% on the performance of PVT systems. Outdoor experiments were run with volume flow rate of 0.5 L/min for the aforementioned nanofluids and distilled water as a reference fluid. The study results, which were analyzed from energetic and exergetic viewpoints, have shown and revealed that the MWCNT-water nanofluid presented a better performance in terms of photovoltaic energetic conversion compared to graphene nanoplatelets-water nanofluid and distilled water, while graphene nanoplatelets-water nanofluid revealed the highest thermal energetic efficiency. Moreover adding thermal unit to photovoltaic module (PV) enhanced the total energetic efficiency by 53.4% for distilled water, 57.2% for MWCNT-water, and 63.1% for graphene-water. From the exergetic viewpoint, the increase in total exergetic efficiency was 11.2%, 12.1%, and 20.6% for PVT collector cooled by distilled water, MWCNT-water nanofluid, and graphene nanoplatelets-water nanofluid respectively.