The design and operation of an electrodialysis desalination process are based on a set of fixed and variable parameters such as stack construction, feed and product concentration, membrane properties, flow velocities, current density, recovery rates, etc. These parameters are interrelated and may be rather different for different applications. For an efficient operation of an electrodialysis desalination plant, the process has to be optimized in terms of overall costs considering component properties and operating parameters. In this study the design and optimization of an electrodialysis plant to be used for brackish water desalination has been treated. The required equations were derived or, as in the case of the limiting current density, were experimentally determined. As an example, an electrodialysis plant with a sheet-flow stack construction and given feed solution composition was designed and optimized in terms of overall costs and the sensitivities of the different parameters are analyzed.