In the present paper, efforts has been made to study the thermophysical performance (properties) of N photovoltaic thermal flat plate collectors coupled with double slope solar still (N-PVT-FPC-DSSS) and operating with helically coiled heat exchanger. The analysis has been performed for the optimized concentration of NPs (Al2O3 0.107%; TiO2 0.093%; and CuO 0.131%) and optimized basin fluid (base fluid/nanofluid) mass (50 kg) for different weather conditions of the month May (New Delhi). The Nusselt number (Nu) and Rayleigh number (Ra) are functions of thermophysical properties of nanofluids and strongly influence the natural convective heat transfer coefficient in the solar still. Therefore, these numbers have also been investigated for base fluid and Al2O3, TiO2, and CuO–water-based nanofluids in detail. Significant enhancement in natural convective heat transfer coefficient (Al2O3 67.03%; TiO2 63.56%; and CuO 71.23%) and Nusselt number (Al2O3 119.72%; TiO2 98.64%; CuO 151.62%) has been observed. The monthly productivity of the hybrid system found to be higher by using nanofluids (320.77 kg TiO2; 338.23 kg Al2O3, and 355.46 CuO) as expected from the heat transfer results. Moreover, the comparative study between the proposed hybrid system and passive DSSS has been carried out.