This paper illustrates a proposed design to the Center for Solar Energy Research and Studies (CSERS) - Tajura, for the erection and testing of a stand-alone photovoltaic (PV) system for the powering of a small scale seawater reverse-osmosis (SWRO) desalination plant. The plant promises to deliver up to 0.25 m3/hour of potable water from seawater with a salinity of about 38,000 ppm and the osmotic pressure of 26.4bar. In the current paper, ROSA Software by Dow chemical company was used to establish suitable membrane unit at this capacity. A unit of 4 inch of SW30-4040, with a feed pressure of 48 bar, and a salt recovery (R) of 20% with total dissolved solids (TDS) of 190ppm was selected. Also results showed that, the electrical consumption of the SWRO plant was 2500 W, and the specific energy consumption was 10 kWh/m3. The size of the selected stand-alone photovoltaic (PV) system to power a SWRO plant with a mean production capacity of 1.5m³/day (6 hours operating per day), is 48V nominal voltage, 72 PV modules (shell SQ85-P), and 16 batteries with the capacity of 383Amp-Hour each.