Sell Your Unused Car Battery Power; Save the Planet

Vehicle-to-Grid technology, which would allow electric vehicles to send excess battery charge back to an electrical grid, has the potential to be an income-generating source for drivers, since it would be cheaper for grid operators to buy back power from electric vehicles than it would to build battery stations that generate the equivalent amount of energy. Ralph Orlowski/Reuters

It may soon pay to drive an electric car. Literally.

As power grids rely increasingly on renewable energy, storing excess power is going to be ever more essential. Solar and wind energy are intermittent sources of electricity, often producing a surplus when they're in full swing, and zero when nighttime comes or winds die down. So grid operators need ways to store excess capacity in down times and tap into it when they need it.

They could build huge warehouses crammed with battery packs for storage, but that would be costly. A much less expensive solution is what's called vehicle-to-grid (V2G) technology: a computerized system that enables owners of electrical vehicles (EVs) to send some of their cars' stored battery power back to an electrical grid—and get paid for it.

One EV battery's capacity is around 10 kilowatt hours of power. So just 30 cars would provide enough power to run around 300 homes. As the number of EVs on the road grows to hundreds of thousands to millions, the potential to store massive amounts of energy in a fleet of EVs is vast. That energy is also very cheap: According to Willett Kempton, who oversees a University of Delaware research team that has pioneered the V2G process, buying power from EV batteries would cost grid operators just a tenth as much as building battery stations with equal amounts of energy.

Earlier this year, Nissan announced it was working with the Spanish utility company Endesa to roll out a V2G system. Meanwhile, Danish startup Nuvve, which has licensed V2G technology from Kempton's Delaware team, is expected to begin commercial operations with two European grid operators and two global automakers during the first half of next year.

An automated system would take power from EV batteries when it's most needed by the grids and at a good price for buyers and sellers. If owners need to take a long trip and can't risk giving up any battery capacity, they could override the system to temporarily stop a grid feed. Kempton says that owners could even earn more from V2G than what it costs them to keep their batteries charged. "The proposition," he says, "is pretty compelling.