We're about 3 orders of magnitude away from green hydrogen being reasonably described as "at scale" at this point. It's roughly where PV was 15-25 years ago: nice to see the effort going on, but not at scale.

I would like to see some home system that makes and stores H2 with excess PV — such a thing certainly feels like it should be possible, given how easy hydrogen is to make, but I'm not a chemist or a civil engineer, so I'll leave that to those who know what can go wrong and how to fix it.

Such product exists and it has been installed at several sites: https://www.homepowersolutions.de/en/picea-plus/

Nice! Thanks for the link, hopefully they do well.