The issue with this line of thinking is that electrolyzers are very expensive. I've read papers that estimated that using free electricity would only be cheaper than running 100% on the time for normal electricity prices of 8-9 ct/kWh (in germany) if free electricity was available at least 25% of the time. With energy storage for the daily variations already shaving some of the peaks off, I expect this to be surprisingly little energy (not even covering applications where hydrogen usage is pretty certain based on the lack of great alternatives).