This is a fantastic idea, and it’s a no-brainer, really, that all electric cars should have the ability to power the grid, rather than just drawing power from it. The number and size of power plants is a function of peak electricity demand; if electric-car owners collectively can help meet peak demand, then that means we need fewer power plants. And, the revenue from selling that electricity would help offset the extra cost of buying an electric car in the first place.The comments point out two things. First, constant charging and discharging of a car battery would significantly decrease its useful life. Second (by yours truly), in most states, regulations prevent utilities from charging residential customers different prices for electricity at different times of day, so the financial benefits or charging off-peak wouldn’t be be captured by users.
Then Dan Ferber, the author of the original article that was the subject of Felix's original post, clarifies that the vehicle-grid interaction is mainly frequency regulation, not bulk power - very helpful!
The problem with comments, though, is that people lose interest or stop checking. So my final question - "if the main vehicle-to-grid interaction is frequency regulation, rather than bulk power transfer, then it’s unlikely to lead to the type of load-shifting and peak-shaving that Felix suggests, correct?" - has, as of now, gone unanswered.