I would bet on desalination becoming practical using solar power, before fusion is cheap enough to compete. The day/night cycle isn't a problem for desalinatio

I would bet on desalination becoming practical using solar power, before fusion is cheap enough to compete. The day/night cycle isn't a problem for desalination because fresh water is easy to store, and the places that most need water tend not to be cloudy. I think the killer app for fusion is large vehicles: cargo ships, spacecraft, helicopter islands, etc.