A driveway in suburban Massachusetts holds an electric car that is doing something unusual this week, sending power backward.
Instead of only pulling electricity from the grid, its battery is feeding some back out.
A utility app on the owner’s phone shows a small credit landing in the account.
No generator started, no new power line got built, no plant burned extra fuel.
The only thing that moved was the electricity already sitting in a parked car.
So how does a car battery end up acting like a tiny power plant for the whole neighborhood?
How a parked car turns into backup power for the grid
The mechanism is simpler than it sounds. A bidirectional charger lets electricity flow two directions through the same plug, so the same cable that fills a battery overnight can also drain a slice of it back into the house or the street during a late afternoon demand spike. The car becomes a mobile power source that happens to also have wheels.
Utilities call this vehicle to grid, or V2G, and the trigger is almost always the same few hours. Air conditioners, the first wave of school runs and shared appliances all draw power at once on hot summer evenings, and that short window is what utilities normally cover by paying a natural gas peaker plant to switch on for an hour or two at premium prices.
A V2G program flips that math. Rather than paying a power plant operator to burn fuel, the utility pays a driver a few dollars to let a software platform pull a slice of their battery’s charge during that same window, then top the car back up later when power is cheap and demand has eased.
That is the trade now running in eastern Massachusetts, where two of the state’s largest utilities launched a test built on top of an existing demand response program. The car does not need to be driven anywhere or touched by a technician; a connected charger and an approved vehicle do the rest automatically once a driver opts in.
What the pilot actually looks like on the ground
Enrollment so far is narrow by design. The program folds V2G into Eversource and National Grid’s existing ConnectedSolutions offering, and it leans on a short list of named technology partners, including EnergyHub, Sunrun and The Mobility House, to manage the software side of things.
Only a handful of vehicle models currently qualify nationwide, and the pilot itself started with just 45 cars, which keeps the program small while engineers watch how real batteries hold up under repeated export cycles. That caution matters because other early V2G pilots around the country have similarly limited their vehicle lists to a small handful of approved models, a reminder of how selective these programs still are nationwide.
Even so, the scale of potential supply is large. Massachusetts already has well over 100,000 electric vehicles registered on its roads, and the number of bidirectional capable models reaching dealer lots keeps climbing every season.
Each one sitting idle in a driveway for most of the day is, in effect, unused grid capacity. That idle time is exactly the resource the pilot is trying to capture, the same way GCN has covered how a New York utility already shifts charging off peak without any power export at all.
Why utilities think this beats building more power plants
The hardest numbers so far come from industry estimates rather than years of billing data, since the residential pilot itself is still brand new. A vehicle to grid study commissioned by General Motors and conducted by the energy modeling firm E3 found that two way charging could deliver five to 15 times more value per electric vehicle in many electricity markets than one-way managed charging , a gap utilities say justifies the extra equipment cost.
That estimate lines up with why utilities elsewhere are racing in the same direction. In California, one municipal utility opened a vehicle to grid pilot for commercial fleets, built specifically to capture unused battery capacity and send it back to the grid during tight hours.
In Michigan, an automaker is running a similar bidirectional trial with a small group of its own employees’ cars. Peak summer afternoons are the real stress test, and that is precisely when a grid operator’s most expensive generation gets dispatched.
Replacing even a fraction of that output with parked cars means fewer hours spent paying premium peaker prices, a saving utilities argue eventually shows up on everyone’s bill, not just the EV owner’s. Elsewhere, grid scale batteries have already proven how fast stored power can blunt a price spike.
Where the idea still runs into real limits
None of this comes free of friction. A recent industry certification program from UL Solutions, built around a new supplement to its UL 1741 standard, exists specifically because utilities, automakers and regulators still need a shared safety standard before export equipment can scale much beyond pilot size.
Vehicle compatibility remains the biggest bottleneck. Most electric cars on the road today, including some of the best selling models in the country, simply cannot export power at all without aftermarket hardware, which keeps the pool of eligible drivers thin no matter how generous the payment.
Battery wear is the other open question. Automakers are still working out warranty language for packs that cycle more often than a normal charge and drive pattern would require, and some manufacturers have yet to formally bless the practice for every model line.
Even the most optimistic backers describe this as early stage. Coverage of the V2G rollout has quoted industry figures calling the underlying flexible demand concept still new to the grid, language that signals promise more than proof.
What a wider rollout could mean for drivers and bills
If the Massachusetts pilot grows the way other EV programs in the state have, the path forward looks less like a single dramatic announcement and more like the slow widening of an eligible vehicle list. Every additional approved model adds a few thousand more potential participants without any new wires in the ground.
That slow build mirrors what happened with ordinary managed charging, where a Maryland utility grew a program from under 7,000 drivers to 30,000 once regulators signed off on making it permanent. V2G is simply the next rung up that same ladder.
For an ordinary driver, the appeal is straightforward even if the technology underneath is new. A car that already sits parked most of the day earns a small monthly credit for doing nothing differently, while the utility avoids paying for an hour of expensive backup generation.
Whether that trade scales past a few dozen driveways depends on vehicles, warranties and standards catching up to the pilots now running. For now, the lights staying on during the hottest hour of a summer evening owe a little more to parked cars than most drivers realize.
