Water and energy are two key factors in human life that always control the growth and development of human societies. Climate changes, increasing the population in urban areas and industrialization, have increased the demands for freshwater around the world. Estimates show that a small percentage of all freshwater produced in the world is from renewable sources. By developing the technology, lowering equipment prices and increasing attention to the environmental problems of fossil fuels, utilizing renewable energy is growing. By providing a wide variety of conventional desalination methods driven by various types of renewable energy technologies in the world, water and energy legislators should choose different methods to meet the needs based on the local potentials by paying attention to the desalination processes and power systems. In some cases, concentrated solar power for thermal desalination or electricity generated by the photovoltaic plants for membrane desalination systems can be used in arid areas. Definitely, the most problem of using renewable sources is their unsteady natures, which using storage systems or combining with other renewable sources can solve this problem. This chapter provides extensive information about renewables, desalination and performance analysis of power systems. Reverse osmosis technique is a practical process in desalination which 69% of desalination plants use this system. Solar energy is an important source of energy for hybrid systems. The geothermal has a steady performance at a specified depth. Ultimately, obtained results from energy and exergy analysis would have provided a better insight.