Lanzarote, one of the Canary Islands, pioneer in Spain of seawater desalination systems with a considerable multiprocess desalination capacity, had arrived to the point where some of the installations were obsolete, with systems that either due to their high energy consumption or simply because they were at the end of their life cycle, were only being use for water consumption peaks due to the touristic seasons. As a consequence, a new RO plant with a 20,000 m(3)/d capacity was planned and tendered. This new plant had to provide low salinity water (50 mg/l) at a recovery in the range of 50% and this with the minimum energy consumption. This paper presents the winning concept for the plant which was constructed and started-up at the end of 1999: Lanzarote IV. The plant uses the new FILMTEC (R)* high-capacity element (non-HR) SW30-380 in the first pass and the low-energy membrane FILMTEC (R) BW30LE-440 in the second pass. The paper presents the operating parameters and compares these with conventional SWRO plants.