Well, what energy where and at what cost? It's possible that there will be renewable overbuild to the extent that there are enough times of cheap or negative energy prices, especially in sunny locations, that can be used for fuel creation.

(The downside I must mention is that high capital cost low utilization low running cost => still high cost)

The USN have a solution in their back pocket: https://www.zmescience.com/research/us-navy-synthetic-jet-fu... , presumably for at-sea refuelling using surplus energy from the reactors of carriers.