Batteries do make sense in some situations where you have large amounts of renewables available on the local grid, and parts of Australia and California are paying homeowners incentives for installing local storage. They make less sense immediately in places where you have hydro and nuclear as base load along with renewables; the capacity factor is already accounted for, so you'd want to prioritize anywhere you could displace fossil generation (such as natural gas).

Tesla is also pioneering virtual distributed load systems, where they can have a utility send a signal similar to that used to shed AC units during high consumption periods, but the signal is instead used to command vehicles to charge when there is excess energy on the grid. [1] This would make sense today in places like Texas, that have so much wind energy (and not enough transmission capacity to other load centers) some utilities provide you electricity for free at night. Any KwH you can use instead of curtailing is a KwH of energy you're not wasting.

[1] https://electrek.co/2015/08/16/the-power-of-controllable-cha...