Abstract
The desalination plants in Saudi Arabia are of dual purpose, water/power production. The production ratio of these plants does not essentially reflect the real demand for water and power. Power must be consumed as it is produced since it is not efficiently stored. The storage of excess water requires both extra production cost and storage expenses. The design plant must be operated with certain capabilities for off design performance. The operation of a dual purpose MSF desalination plant that reflects the fluctuations in water and power demands in certain locations has been investigated.