V2G is an ingenious way to fully utilize the capability of an EV. V2G isn't about increasing range or improving charge times; V2G is a way for EV owners to make both money and a difference in the green scene.
When an EV is plugged in to the energy grid, either at home or at a public charging station, it pulls energy at whatever rate the utility company charges at that time of day (less at night, more during the day). But, imagine if the car-to-grid system knew when the car wasn't going to be used again until the following day. It could actually sell back any remaining energy stored in the battery to the utility company--hopefully at the higher day rate--and wait to charge at lower nighttime rates. Research being conducted at the University of Delaware has valued V2G to the EV owner at up to $4,000 per year. Benefits increase when V2G is operating with a localized renewable energy source (wind, solar, etc.).
The major roadblock to jumping off the grid for local renewables (personal windmills or solar panels) is the inconsistency of energy. Wind gusts aren't consistent, and when it's cloudy out solar isn't too helpful. This is where V2G comes in with another use: buffering energy. When the sun is out and a solar panel is operating at maximum, the energy coming in can be used throughout a household, with excess sent to the vehicle's battery for storage and later use. Today's car batteries can store nearly 50 kWh (Tesla Roadster), which is more than enough to run a home at night leaving plenty of range left for the next day's commute.
Vehicles doing it now
Before the Chevy Volt came out, there was a lot talk from GM saying how they wanted the Volt's battery to "have a life outside the car". They said that the Volt would have V2G capability. However, since the launch we haven't heard much more about that.
Interestingly, Nissan just recently showed off their plan to make the Leaf part of a V2G system in Japan. And it couldn't come at a more critical time. Ever since the March disaster that took out the Fukushima Daichi nuclear power plant followed by several others for safety checks, there has been an enormous energy crisis. Nissan plans to take their V2G commercial by as early as spring 2012.
This V2G use case will likely replace the need for small generators used during a power outage. If an EV senses a power drop, it can send power back to the home from the battery instantly, acting like a massive battery backup.
Another interesting idea comes from range extended EVs, like the Chevy Volt. If a home's power were to go out, the Volt could run its gasoline engine to create electricity. As long as there was gas in the tank, the house could run vital appliances.
A lot of future potential
The whole idea of what an electric car can do is still evolving. GM got it right when saying the most valuable asset of an EV is the battery; there are a lot of uses during and after the car's life. Much of the criticism for V2G comes from concern over using the batteries more often, thus reducing their life. But, as modern batteries become more advanced, some researchers are saying that the cells can still hold a charge for nearly 55 years--even after V2G. To what capacity is still unknown.
Before V2G gets big, utility companies and automakers have to setup communications system with smart hardware and software to network EVs to the grid. There are a few utility companies participating in trials to test out the concept. In fact, the Pacific Gas and Electric Company has teamed with Google to convert a fleet of Toyota Prius' to be V2G PHEVs for testing.
Utility companies love it
When an EV is able to charge at night and sell energy back during high-demand times, utility companies don't need backup power plants for peak-energy demands. If there were enough EVs distributed, the extra energy needed could come from the car, further reducing carbon emissions. Also, like local renewable energy sources, V2G enabled EVs could become a buffer for utility companies. There are a lot of options. Once agreements are struck between the different sectors, it all comes down to the software and what the car owner wants to do.
EVs have many more uses than simply reducing the amount of gasoline purchased. They have the potential to optimize the flow of electricity in an extremely efficient manner. When most cars sit idle in the garage 95% of the time, whey not put them to work?