Sure, but assuming all of the office buildings of the world don't retrofit their parking structure with grid connections, these cars will only be connected to the grid in the evenings. I suppose this would be great for taming the dinner time spike, but it seems to put the availability, for them to store excess, where it's needed least: https://www.researchgate.net/figure/California-daily-utility...
Why would you assume that no office building would retrofit their parking structure when there are huge incentives to do so?
For sure not all of them might, but if enough do, it will be a major benefit.
But yes, if a car isn't connected to the grid it cannot participate.
I'm definitely not assuming that none will, I'm just assuming it will be a some smallish fraction for the foreseeable future. Nearly 50% of California's working population works for small business. It's not just the cost of the equipment, but also cost up upgrading the panels and, almost certainly, service lines.
Where I am (a city in California), you have to pay for replacing the service lines/conduits, including digging it up/repairing the street and sidewalk, even if they run 1 city block.
