Abstract Energy consumption has always been of prime concern to the equipment designer. With today's energy costs accelerating at an unprecedented rate, energy efficiency of desalting equipment is getting even more attention. However, local conditions have a considerable effect upon the ultimate selection and design of almost every desalting plant. Once these have been taken into account, by establishing the economic optimum and desired safeguards for the specific local conditions, energy efficiency of the desalting equipment usually is considerably less than the maximum that conceivably could be achieved. One finds that the inventors' and designers' efforts to reduce energy requirements certainly have not been in vain but, on the other hand, can be severely diluted by compromises necessitated by local conditions. This paper explored some of these conditions and their effects upon the energy efficiency of seawater desalting plants for the three major desalting processes: Vapor Compression, Multistage Flash, and Reverse Osmosis.