Continuous elevation in temperature of photovoltaic (PV) panels results in the decline of PV electric power production. This paper presents the experimental methodology tested outdoors in Taxila, Pakistan to lower PV temperature with the simultaneous use of nanofluid (graphene/water) and phase change material (RT-35HC). Performance of this hybrid PVT system in terms of PV temperature, electrical efficiency, thermal efficiency and overall efficiency, is compared with PVT/PCM system integrated with water flowing through tubes inside PCM, PV/PCM system and conventional PV. Effects of varying volume concentrations (0.05%, 0.1%, 0.15%) of graphene nanoparticles as well as flowrates (20, 30, 40 LPM) are also examined and it is found that the best performance is achieved with 0.1 vol% nanoparticle concentration and 40LPM flowrate. From the experimentation results, maximum reduction in PV temperature is observed to be 23.9 degrees C, 16.1 degrees C and 11.9 degrees C with nanofluid-based PVT/PCM system, water-based PVT/PCM system and PV/PCM system respectively, with maximum enhancement in electrical efficiency of 23.9%, 22.7% and 9.1% respectively as compared to conventional PV. It is also found that nanofluid-based hybrid PVT/PCM system shows 17.5% higher thermal efficiency as compared to water-based hybrid PVT/PCM system, and overall efficiency enhanced by 12%. Thus, results ensure the best performance with hybrid PVT system integrated with nanofluid and PCM simultaneously. (C) 2019 Elsevier Ltd. All rights reserved.