A question often asked in the SWRO industry is: 'How do I select the best energy recovery device for a reverse osmosis plant? This paper explains the most important points to be considered when installing a work exchanger energy recovery system. The basic plant design has to be different to fully benefit from the advantages a work exchanger system offers. A train or centre design for plant layout has to be selected at an early stage.. and if a train design is planned the optimum size of the trains can result in significant savings of both initial investment and energy consumption. This paper explains how to optimise the overall power consumption of a plant, to reduce the capital costs and to evaluate the most economical energy recovery device. Besides the main advantage of the inherently higher efficiency of a work exchanger energy recovery device there are other operational advantages compared to other energy recovery devices such as the Pelton turbine, pressure exchangers and so-called turbochargers. In order to illustrate such differences the paper explains how to operate and control a plant with a work exchanger based on the example of the Singapore project.