That’s kinda why Tesla is doing what it’s doing. I’m not sure the exact production, but it looks like nearly 4 GWh in fixed storage last year, and at least 50 GWh (0.93 megacars * 54 kWh smallest battery) in their cars required the ability to rapidly make factories that can make batteries that could also be used in grid storage (I’m assuming making the batteries is the hard part of both electric cars and grid storage, if I’m wrong about that it breaks my argument).

(And inter-season storage is too high a threshold: not many people are living in the artic/antarctic circles away from grids connecting them to places that still get some sun even in winter).