Not sure I agree with the idea that grid-scale batteries are not the solution. Looks at what Tesla has been building in places like Kauai, HI and Australia. I've never been crazy about the car idea and see two problems with it. One is simply people might not want to feed power from their cars back to the grid as they might want the range to jump in their car and go anytime. Also I've heard that that's not really what car batteries are designed to do and that it would likely degrade their longevity rather fast. Flywheels may also be part of the picture.,(reply>), If your car had 90% charge left when you got into it, you'd probably be alright with that. Just configure the car's computer to only use the top 10% for grid-balancing, or let it go beyond that if the car's in a situation where it's definitely not going to get used for a while (like you've arrived home from work and don't plan to go out again until the next morning, so the car can charge overnight while power is cheap).