I agree that hydrogen efficiency doesn't matter here, but the capital expenditure to build a giant electrolyzer with 5% utilization doesn't really make sense. The cost of the electrolyzer is the things that needs to greatly fall if hydrogen is going to be used for long-term storage.

Electrolyzers driven by otherwise curtailed renewables would have a capacity factor much higher than 10%. If I go to https://model.energy/ and solve for the optimal solution for the US for 2011 weather and 2030 cost assumptions, the capacity factor of the electrolyzers is 43%.

That is more of a what-if. If there was more wind and solar built out there would be enough curtailed energy to run electrolyzers at 43% capacity factor. I am saying today it doesn't make sense because there isn't a lot of over-provisioning taking place. There should be but what investors are going to jump first with a curtailed energy electrolyzer when curtailed energy is low.

It's a demolition of your nonsensical 5% number (which is also what-if).

In the state with the most solar built out in the US the curtailment is 5% https://www.eia.gov/todayinenergy/detail.php?id=49276.

Which is of course meaningless, since curtailment increases with the amount of installed wind/solar. What matters is how much curtailment there would be in an optimal all-renewable energy system.

I tell you what: show me a cost optimized renewable energy system in which the electrolyzers have a capacity factor of 5%.

Hydrogen has important industrial uses. Currently we get it from natural gas. That has to change in the future.

Hydrogen produced using NG will be deeply undercut by electrolysed hydrogen. Extracting NG will become unsustainably expensive as zero-opex synthesis surges.

Demand for hydrogen for all uses will drive elecrolyser use to as close to 100% as available energy permits. Ultimately, other cheap storage will be used to drive them.