Desalted water is the source for thermal and nuclear power stations. Sea water is desalted in many cases if power stations are located on the sea shores. The operating types of reverse osmosis systems and thermal desalting installations don't meet the requirements for the water quality for power stations. Additional water desalting is required. The possibility of combined desalting installations application is considered in this paper. These installations include membrane systems at the first stage and thermal systems for water desalting at the second stage. Different schemes of combined desalting installations have been considered. The methods of optimized calculations of such systems have been presented. The parameters of desalting processes which provide the required quality of desalted water have been determined. The paper includes some recommendations for combined desalting installations application for thermal and nuclear power stations.