Most localities will store no more than two weeks' production. If local banked energy looks likely to get used up, and incoming transmission line power cannot be secured, they order a shipment of synthetic fuel (ammonia) from a solar farm in the tropics, or from a wind farm somewhere else. (Until those come online and undercut NG, they will burn NG.)
Expect most places that do buy batteries to buy no more than 4 hours' worth. Other media will be cheaper, beyond that.
If they need to keep the old combined-cycle turbines ready to spin up anyway, they are likely to favor banking a couple of weeks' fuel for those. They might install fuel synthesizers, but probably most will sell excess to the grid, which will absorb any amount, at the right price.
I hope they get the economics to work.
Also the longest duration flow battery in the Wikipedia article runs 10 hours. We really need something that can charge for months in the summer and discarge for months in the winter. Maybe rust https://news.ycombinator.com/item?id=27944600 or aluminium https://news.ycombinator.com/item?id=26463249 ?