Not enormous, but not insignificant either.

But are they more or less than reverse osmosis?

If energy becomes "free" does it matter? If solar continues on its current trajectory, there needs to be some kind of sink to utilize the energy or it is all going to turn into bitcoins.

+1

The "fully charged show" sometimes have videos on this and similar topics. This [0] video goes through the pros and cons of using hydrogen in different ways

My takeaway is that as much of the energy as possible should be used without converting it. This avoids the substantial losses converting to and from hydrogen. But storage is one of the viable uses.

[0] https://youtu.be/MgmBkvrO0Dg?si=8c-y3naRRH65O4Lb