Granted, I'm taking the word of someone who is a hydrogen promoter.
But... since one of the methods is to use electricity at night which right now is thrown away. It would seem to me that hydrogen produced by that method is basically "free". Likley, there wouldn't be enough surplus power this way, but as other posters have pointed out, there are many ways to skin this cat.
And right now, I so want to unplug from the Saudis. I'll even take some effort and expense on my own to do my little bit.
Enough said.
But... since one of the methods is to use electricity at night which right now is thrown away. It would seem to me that hydrogen produced by that method is basically "free".
Did your "hydrogen promoter" also tell you this falsehood?
The nice thing about hybrid cars is that they are here now. Of course, if they would also "plug in" to the grid, that would be all the more better.