Using Hornsdale as the prototype, V3 may well have extra storage capacity that could serve a grid stabilization function, thus absorbing power at times when the cost is negligible/negative and delivering power during peaks. The only limitations on that approach, I think, are first, Supercharger demand may sometimes coincide with peak utility demand and second, the ultra-quick responsiveness of grid services supplied by battery packs is far faster than the fastest tarrif structures for grid services, normally, that is.
For more detail and factual backup:
Hornsdale Power Reserve
This is the major prototype that shows how Tesla and others are having monumental impact transforming grid services, specifically by rendering peaked plants redundant and overpriced, regardless of location or alternatives, and with zero need for subsidy. Part of that is the ability of these installations to take power when utilities are overproducing, being paid to take the excess and also be paid large prices for supplying the same electricity when the utility has a deficit of production. That, by the way, is precisely why so many utilities are rushing to install battery storage facilities.
Net: Tesla can and almost certainly will, use future Supercharger installations as grid services supplements, thus reducing their costs and also generating potentially large revenues.
