In PG&E's case the project fizzled out completely after automakers expressed concern that supplying power to the grid—not just drawing it in—would prematurely wear out car batteries and force their early replacement, a company spokesperson told InsideClimate News. The battery used in most E.V. models costs $16,500—nearly half the cost of the vehicle and up to eight times more expensive than the lead acid batteries used in gas cars, say estimates.
The PG&E project also faced policy hurdles. Federal regulations do not allow individual drivers to sell battery power on the wholesale market, a limitation that still needs to be adjusted if eV2g is to expand to consumers.
While U.S.-based demonstrations move forward in fits and starts, several international projects are also progressing, including another venture led by the University of Delaware. Kempton co-founded and serves as chief technology officer for Nuvve, a Danish technology company that is deploying the university's patented V2G technology in a pilot of about 30 cars that can sell power back to the grid.
In Japan, Nissan introduced a new system for its Leaf this summer that would enable owners to connect their cars to a charging outlet and provide electricity to their homes.
U.S. utilities and researchers have yet to model a commercial-scale project using hundreds or thousands of E.V.'s on the ground—precisely what the eV2g venture aims to do.
Why Launch Now?
David Weir, director of the University of Delaware's Office of Economic Innovation and Partnerships, said that a main driver for launching eV2g now, after years of technology development, is the increase in renewable energy sources. The question of how to store renewables is a growing concern for grid operators looking to stave off blackouts and reduce instability caused by surges and sharp drops in clean power supplies.
The rise-and-fall nature of wind and solar "has added to the value of being able to access electric storage devices" to help balance the grid, Weir said. "Every invention has its time, and it looks as if ... the time for considering electric vehicles as part of the grid has probably arrived."
He added that NRG's endorsement of V2G technology could be critical to widespread adoption of the technology.
"You have a large commercial enterprise with credibility in the industry saying that this could be a very important development," he said. "That adds a tremendous amount of credibility to the whole initiative."
Some industry experts, however, remain skeptical of V2G's bankability just yet.
"It is not what I would call a compelling value proposition that would lead the kind of large-scale private investment that [is needed] to really take off," said John DeCicco, a senior lecturer at the University of Michigan. DeCicco was previously senior fellow of automotive strategies for the Environmental Defense Fund, as well as the transportation director for the nonprofit American Council for an Energy-Efficient Economy in Washington, D.C.
One reason is that E.V.'s will remain too niche of a market to be worth it, DeCicco said. He estimated that the adoption of electric vehicles by consumers is likely to remain low due to their high costs, especially as increasingly fuel-efficient and cheaper gas-powered cars come to market.
The relatively small number of drivers who do end up buying E.V.'s won't be large enough provide the scale of battery storage needed to make V2G technology worth the investment for automakers or power companies, he continued. "Trying to advance vehicle-to-grid technology at any large commercial scale is putting the cart before the horse."