Abstract Photovoltaic driven decentralized reverse osmosis plants for brackish water desalination offer a sustainable and low-emission solution for water deficiency problems, especially in arid and semi-arid regions. However, the primary challenge for this combination is how a brackish water reverse osmosis desalination (BWRO) plant based on photovoltaics (PV) can be operated continuously with high energy efficiency. Therefore, this study presents an innovative concept for a BWRO plant operated 24 h/d with a constant drinking water production capacity based on PV and pumped storage as hydraulic energy storage. The latter is used to cover the hydraulic energy consumption of the BWRO process completely or partially in times when the necessary electrical power cannot be provided by the PV plant due to missing solar radiation. During the course of the year, only 2% of the hydraulic energy to be stored in the pumped storage is lost during charging and discharging. The overall efficiency (from PV electricity to used hydraulic energy) of the pumped storage in the investigated innovative system is 78.4%. This value is 2.4% higher than the overall efficiency for a battery system with a high pressure pump in the current designs for BWRO based on PV and battery.