I was thinking that most of the advantages of "vehicle to grid" ie. grid stabilization could be gained without actually drawing on the battery. How? Simply by temporarily shutting off power. Lets say that the grid does not have enough power to meet demand and needs "x" seconds to get the extra supply. If electric vehicle charging was more popular than it is now, then the utility could simply tell the chargers (via internet) to self-shutoff for x seconds. The effect on the grid would be the same as if a similar number of vehicles had supplied that power, except that for those x seconds the vehicles would not have been charging. In the reverse situation, where the grid has too much power and needs x seconds to adjust, then the cars which are at 80-90% SOC can take up the excess power. You might say, what about storing extra solar power? Well the cars can store the extra power by leaving some space in the battery and charging when "extra" power is available. The energy can be dissipated by driving and does not need to feed back into the gird. The same concept could be applied to heating and cooling systems, allowing them to raise (in the case of heat) or lower (in the case of a/c) to suck up excess power and/or temporarily reduce demand. There's no need to store solar power for night-time usage when you have 30-40% natural gas or coal usage. Instead, drop the gas usage by 50% and better manage the energy demand. There's no reason to be cycling car batteries just so that you can run an extra gas plant along with your solar. Obviously, using batteries to store solar/wind power is a great idea for the future when (hypothetically) you have enough solar/wind to cover all the day's usage, but batteries like Tesla's experiment in Australia don't really need to exist to balance the grid when the same thing could be done by cutting off a large demand customer(s). Storing solar in car batteries for night usage would work for some people who have extra range for long trips only, but as long as you have 40% of power by natural gas there's no real need for it.