In the present study, an experimental and mathematical analysis was performed in a novel nanofluid-based collective cooling consisting of inner-plate heat fins in order to explore a photovoltaic-thermal (PV/T) system efficiency for Al2O3, TiO2, and CuO-based nanofluids. The electrical efficiency increase, temperature decrease in the panel surface, thermal efficiency increase, and heat transfer performance of Al2O3-water, TiO2-water and CuO-water nanofluids which were prepared in three different ratios (0.2%, 0.4%, and 0.6%, in mass) and constant fluid flow rates were investigated. The highest electrical efficiency increase was observed in the 0.2% nanofluid Al2O3-water, at amount of 1.467% that correspond to 5.49% increase rate. The highest panel temperature drops were observed at the rate of 0.2% nanoparticles of Al2O3-water, TiO2-water, and CuO-water. The highest thermal efficiency was observed in the Al2O3-water nanofluid with 0.2% nanoparticles as the amount of 49.59% in average. For 0.2% nanofluid cooling, the averages of panel temperature drops were 13.28 oC, 11.64 oC, 11.06 oC, and 9.14 oC for TiO2-water, Al2O3-water, CuO-water nanofluid cooled panels, and water-cooled panel, respectively. Finally, appropriate amount of nanofluid cooling not exceeded 0.4% can be recommended in practical application for its benefits on improving the efficiency of system.