Just for the sake of anecdote, my state in Australia has both a desalination plant and a hydrogen plant, one was a government project to protect the state's water supply and the other was a private initiative to supply "green" hydrogen to steel plants and other heavy industries as they move to a different steel process.

So those are good uses of off-peak power when your local economy is already interested in having those things. The state also has some other initiatives to use the excess generation, such as residential water heating and EV charging using "smart grid" sockets that take into account the local and greater network's load and generation.