Car Power The German power utility E.ON is working with Nissan on making it possible to sell electricity stored in vehicle batteries back into the grid. France's EDF and Italy's Enel are also working on the "vehicle-to-grid" (V2G) concept, and everyone would now like European carmakers to build the same capabilities into their products. Reuters
A few years ago was this also under discussion in Japan. But I lost track, am not sure if this is still being pursued.
Interesting concept but sounds dumb. Unless you don't drive, what's the point? And if you don't drive, then your batteries are empty.
The point is that energy companies are looking for ways to get a more stable supply of energy. They are being asked (by public opinion) to reduce their reliance on coal and gas fired electricity plants and switch to renewables such as wind and solar. However, wind and solar are not stable sources of supply. Firing up a coal plant takes too long in case the renewables suddenly provide insufficient energy. However, if at that point in time many cars have their battery connected to the system (V2G) then the energy company could use these temporarily as energy source. And refill the battery once their other sources generate more electricity. Of course would the electronics in the car have a limiter to avoid that the grid takes up all energy from the car battery.
And if you drive your battery will be soon empty too. In general cars need electricity, they don't produce electricity. They are connected to the system because they NEED electricity, not because they have too much electricity.
These programs are already taking off in the US (mostly California). Usually you have a set point (e.g. provide power to no less than 50% capacity) so you don't leave yourself with an empty battery.