The other advantage of substation level energy storage is in not having to upgrade the feed circuits. Design for average consumption not peak. Storage and renewables make the edges of the network resilient.
UK Power networks recently completed a 2 year trial of a 6MW/10MWh battery system which was installed as an alternative to adding a 3rd circuit to meet future peak demand of a town. At the end of the trial they produced a projected business case for future deployments of:
