A new study shows they can help the grid without being degraded.

One of the hottest questions among energy nerds these days has to do with the interaction of electric vehicles and the electricity grid. Will EVs remain passive consumers of electricity, like toasters or refrigerators, the way they are now? Or will they be able to communicate with the grid and send power back to it when needed?

The answer depends on both technology and economics. A new study contains reason for great optimism.

First, some quick background.

Grid nerds hope EV batteries will talk to the grid

If recent forecasts are accurate, the electric vehicle market is about to take off. The latest research on EVs from Bloomberg New Energy Finance (BNEF) — which gets more optimistic every year — now estimates

“that EVs will account for 54% of new car sales by 2040, not 35% as previously forecast,” which means that “a third of the global light-duty vehicle fleet will be electrified by 2040.”

That means tens of millions of batteries floating around, storing electricity while the cars aren’t in use and releasing it when they are.

Theoretically, all that energy storage could be very useful to the grid, which needs all the storage it can get in order to integrate more variable renewable energy. It needs big, steady, long-term storage, for monthly or yearly variations in sun and wind, but it also needs fast, responsive, short-term storage, to smooth out smaller variations of seconds, minutes, or hours — to provide “voltage regulation,” “frequency response,” and other grid services (many of which are now typically provided by natural gas plants, which will have to go soon).

Read more: Vox