Abstract In the northern part of Saudi Arabia (Al-jouf area), underground water is the main water source which can be pumped to the surface using public electricity or diesel generators in remote areas to drive various types of pumps. Then this brackish water is desalinated using reverse osmosis (RO) system to get fresh water suitable for drinking. So, a small scale reverse-osmosis (RO) desalination unit is very common in use for producing fresh water from brackish water. The present study is directed to discuss and test the performance of small RO system with a capacity of 50m3/day used to desalinate brackish water with maximum 2000ppm total dissolved solids, which can be used in remote areas. Two similar small scale RO units have been tested (each unit has production capacity of 50m3/day), to investigate the performance and cost analysis. In addition, the water resources availability and quality in northern Saudi Arabia is included. Also, the higher availability of solar energy is highlighted to be considered in future projects by coupling solar energy with RO system (the annual average solar radiation is estimated to be 5.77 and 7.22kWh/m2/day for horizontal and tilted plane respectively. In addition, the annual average daylight hours are 12h). The results show that, specific power consumptions are 3.99 and 3KWh/m3 based on installed and actual power consumption respectively. Also, from the cost analysis, percentage costs are 49.4%, 28.66%, 8.47%, 8.4%, 5% for labor cost, chemicals cost, electric power cost, fixed cost, and membrane replacement cost respectively. Also, the production cost resulting from the small BWRO desalination unit is estimated to be 7 SR/m3 (about 2$/m3). Finally, comparing the obtained results with the corresponding ones obtained from similar researches showed an acceptable agreement.