The Carlsbad Desalination Plant outside of San Diego produces around 10 percent of the area’s fresh water by pulling water directly from the ocean. Despite there being more than 18,000 desalination plants worldwide, they provide less than one percent of global water needs while consuming a quarter of the water industry’s energy. The two main methods of desalination are distillation and reverse osmosis (RO), both of which have their own challenges and costs. Desalination is considered a viable solution in areas with severe water scarcity, but it remains a complex and costly process compared to other water supply alternatives.
https://practical.engineering/blog/2023/6/28/why-is-desalination-so-difficult