In hawaii they canceled a proposed inter-island power connector because batteries + solar were just cheaper.
Pumped storage is generally a lot more economic and can store a lot more than batteries but it cant be built quite as quickly & is somewhat geographically dependent. It takes 4-5 years to deploy rather than months.
Before a thing has been built, it needs to be built. Do you need this explained further?
The overwhelming bulk of utility storage will not be batteries, because that is the most expensive alternative. Utility storage will be whatever is cheap and locally practical.
