One of the most affordable and readily available energy sources is solar energy. Humanity is in danger due to the lack of freshwater. Finding novel approaches to these issues that make use of solar energy has grown in popularity as a research area. The previous work presented was made to cool solar cells to increase their performance. The reverse-osmosis system is then fed by the cooling water. This study investigated the ideal conditions for cooling water fed into a reverse-osmosis system. Two identical solar cells were used for the current experiments. Water was used to cool one of the two cells. Measurements were made of the cell surface temperature, output voltage, current, and power. It was calculated to find the electrical efficiency of both cooled and uncooled cells. The cooled cell produced a maximum power of 6.75 W, according to the results. At 1:00 p.m., the gain power reached its maximum. The greatest efficiency gain, 50.2%, was observed at 4:00 p.m. Throughout the work that was presented, there was an 8% decrease in cell surface temperature. The water application value engine (WAVE) was used to simulate a reverse-osmosis system. The program’s findings demonstrated that energy consumption dropped as feed water temperature rose. The findings of a case study conducted in a real water-desalination plant were confirmed.