The aim of the present study was to examine the impact of incorporating nanofluids on the operational performance of a flat-plate solar collector-based water heater (FPSH). To this end, three distinct nanofluids were created by mixing Al2O3, CuO, and SiO2 nanoparticles with water in a ratio of 0.5 vol%. The experiments were conducted at a location in upper Egypt, using two different flow rates, 0.0256 and 0.0423 kg/sec. The results showed that the use of hybrid nanofluid as the circulating fluid in the FPSH improved its performance compared to using water alone. The outlet water temperature and overall efficiency of the system were found to be better with the use of the hybrid nanofluid. The highest improvement was achieved when the flow rate of the hybrid nanofluid was set at 0.0256 kg/sec. The study provides evidence for the potential of nanofluids in enhancing the output temperature and thermal efficiency of solar energy collecting devices. This research offers valuable insights into the development of more efficient and sustainable energy solutions for the future. The use of nanofluids in FPSHs can lead to significant improvements in their performance, which has the potential to positively impact the energy sector.