Scarcity of fresh water, forced many countries to get their water needs, or part of it, by means of saline water desalination. Reverse osmosis (RO) systems are useful tools in this concern. In case the grid electricity is not available or costly, photovoltaic (PV) power is necessary to derive RO systems. The present paper is concerned with providing a methodology for complete sizing and design of a photovoltaic reverse osmosis (PVRO) system in Egypt. Egypt has very favorable solar energy. A computer program was constructed to solve the mathematical equations of the model to get the numerical values. The program is capable of calculating the solar irradiation for any city in Egypt. Calculations and selection of the RO system with all connected pumps, the peak PV power needed, and the actual PV area were performed for different water demands ranging from 1-100 m3/day, and various water total dissolved solids (TDSs) of 5000, 15000, and 30000 mg/l. The cost of the complete PVRO system was also determined. The concern of the paper is related to water desalination and solar energy, which are responsible for our existence. The work also aims toward sustainable and clean environment via utilizing solar energy.