It is possible to unlock a 100 percent renewably powered grid — without any coal, nuclear or gas storage baseload — within the next several years.

And any driver or homeowner could contribute to the solution by using electric vehicles (EVs) as mobile batteries that charge at one location when there’s a surge of renewable energy and deliver it back to the grid at another when it’s needed.

The storage potential of EVs is striking. Aggregating energy across one million EVs amounts to 50 to 100 GWh of storage capacity, according to industry analysts Brattle Group. Putting that into perspective, Tesla’s “big battery” in South Australia, currently the largest battery in the world, stores less than 1GWh.

With electric cars storing and transporting renewable power, we wouldn’t need to continue building expensive storage infrastructure. For utilities, this vast mobile power source could be a savior — or their downfall.

Batteries on wheels

EVs have more capacity than they need on a daily basis: The average daily car trip in the U.S. is about 30 miles, while most EVs have a range of 124 to 310 miles. Current base model vehicles with a 186.4-mile range on a 60 kW battery pack could run a typical house, including air conditioning, for four to five days. And despite some car owners’ concerns, discharging the battery won’t cause noticeable wear, because a typical battery’s life is longer than the lifetime of a vehicle.

Using vehicle-to-grid (V2G) technology, which allows vehicle batteries to store surplus energy from intermittent renewable resources like solar and wind, EV owners could power their homes with energy stored in car batteries or sell it back to utilities, balancing fluctuations in energy demand. Using real-time rates, utilities could encourage EV owners to charge up during the day, when there is excess (and therefore cheap) solar energy, and sell back to the grid during times of high demand.

Read more: Sustainable Brands