About 4% of world H2 production is made as a byproduct of chlor-alkali manufacture, which is electrolysis but NOT with the intention of making hydrogen, reads a Linkedin post.
Since about 1/3 of electricity on earth is derived from renewables or nuclear, it is fair in my view to say that 1/3 of 4%, i.e. 1.3%, is “green”-ish. But most of that byproduct hydrogen is not part of the hydrogen market- most of it doesn’t make its way out of the chlor-alkali...
https://mfame.guru/only-one-third-of-world-hydrogen-is-green/