Solar is incredibly cheap and it's a perfect match for desalination because you can scale the water flow based on available power. And the places that need it the most are deserts with a lot of sunshine and empty land. We're at a point where generating power is almost never the issue.

The actual problem is making the desalination tech itself cheap and easy to maintain so poor countries can afford it. Right now it's only a large scale thing in relatively rich and tech advanced states like Saudi or Israel.

Honestly power isn't even the biggest problem with desalination, it's the spectacular volume of brine commensurate with the volume of clean water you are trying to extract: figuring out both how to dispose of it without creating new environmental hazards and constantly repairing/replacing the machinery which must filter and plumb that caustic sludge.

Which is all to say in addition to the crazy energy demands of desalinization, there are also problems that dwarf those.