Steam power plants are usually used for producing electricity and can simultaneously work as a multigeneration plant to produce steam, freshwater, and power. This study performed the optimal combination of a steam power station as the source and a site utility system as the sink of power and steam. Approximating the potential of the cogeneration before designing a central utility system for site utility systems is vital to set goals for onsite fuel demand along with power, freshwater, and steam production. For this purpose, a precise and efficient cogeneration targeting strategy was utilized to couple a site utility of a process and a steam power plant. This study proposed a novel strategy for optimal designing integrated steam power plants and site utility consisting of process station industries. Accordingly, exergy, exergoenvironmental, and exergoeconomic analyses were conducted. The environmental impacts of life cycle assessment (LCA) in exergoenvironmental analysis were apportioned to the exergy streams, pointing out the key factors of the system with the most significant impact on the environment and possible improvements related to them. Besides, the water cycle algorithm (WCA) was employed to optimize the integrated plant. The capabilities of the proposed procedure were implemented to the petrochemical complex site utility and steam power plant. The results showed that an optimum solution was achieved using the new procedure with significantly reduced computation time.