A small-scale photovoltaic (PV) powered reverse osmosis (RO) plant is designed to operate at variable flow/pressure conditions for stand-alone applications in equatorial areas to desalinate brackish water. Two operation strategies for a PV array of 165 Wp (3 modules of 55 Wp) are simulated and compared: Plant I uses two modules for the RO pump and one module for the well pumping; Plant 2 uses the three modules for both applications. A DC-DC buck converter with maximum power point tracking (MPPT) was developed especially for Plant 2. Results show that Plant 2 has a better performance, such as: increase of 60% in the daily permeate production and of 32% in the daily operation period, 1.57 kWh.m(-3) of average specific energy consumption and a PV power-permeate daily production rate of 0.64 Wp.L-1 for a feed water with 800 mg.L-1 of total dissolved solid.