At the scale of the electrical inputs for medium-large scale apartment buildings, the cost to be battery-ready isn’t measured in dollars but in cubic feet you’re reserving for the purpose. The breakers and line (and sometimes full transformer banks) already have to exist to distribute grid to the sometimes hundreds of units of apartment, so converting a standard demarc to one which would support a battery array wouldn’t be more than installing the shunts and electronic controls. 1 afternoon for a 2-3 man team and maybe a bucket truck if you’re feeling fancy.

The problem is that every square foot of floorspace is planned for in these complexes, and there’s a zero percent chance that any builder is going to allocate the raw square/cubic feet to grid storage without the grid operator or city paying cash for it, and maybe not even then.

Now, if you want to try to legislate that all parking must be built on top of batteries or something, that might be workable, but I would consider putting it in the buildings themselves to be untenable.