Massachusetts pilot turns parked EVs into grid-scale batteries as data centers strain the power network

Utilities Are Buying Grid Storage From Driveways

Eversource, National Grid, Sunrun, EnergyHub, and The Mobility House have launched a vehicle-to-grid pilot in Massachusetts that lets qualifying EV owners feed stored power back to the grid during peak demand and get paid for it. The program plugs into Connected Solutions, an existing demand-response framework that already pays homeowners to dispatch residential batteries, smart thermostats, and commercial equipment when the grid is strained 1.

US electricity demand is climbing as data centers multiply and households electrify heating and transportation, while utilities simultaneously replace fossil generation with wind and solar that produce power only when conditions cooperate 2. That combination widens the gap between when energy is available and when it is needed. Flexible storage is the missing piece, and a growing reserve of it sits idle in garages.

The Storage Math

A typical EV battery holds roughly six times the capacity of a residential backup unit 2. Massachusetts has more than 150,000 EVs on the road 1, and most sit parked for the majority of each day. Russell Vare, VP of vehicle-grid integration at The Mobility House North America, a provider of charging infrastructure, called vehicle batteries "the cheapest cost of flexible energy storage that will be available for the grid" 2.

The aggregation model is what makes the economics work. Chip Silverman, director of grid services at Sunrun, a solar and battery company, described the logic: when more batteries join a virtual power plant, each individual car contributes less energy per event, but the collective output grows 2. Only a fraction of owners need to opt in for the grid to benefit.

How the Pilot Works

During a demand-response event, typically triggered by extreme heat or peak evening usage, enrolled EVs discharge a portion of their stored energy to the grid. Owners are compensated, the same way homeowners already earn money under Connected Solutions for dispatching solar batteries and smart thermostats 2. The discharge happens during a small number of peak hours per year, not as a daily cycle 2.

Participants use an app to set their typical driving schedule so the system knows when the car must be fully charged 2. The program pairs V2G with active managed charging, which staggers when vehicles draw power overnight to prevent thousands of EVs from charging simultaneously and spiking demand.

Not every EV qualifies. The pilot requires vehicles with bidirectional charging hardware, and while more models are gaining the capability, the pool of eligible cars is still limited 2. Bidirectional chargers add cost, though Seth Frader-Thompson, president of EnergyHub, a leading provider of clean energy software and services, said he expects V2G to become "dramatically more accessible" as hardware costs decline and standards mature 2.

Fleets Lead the Way

National Grid is separately testing V2G with light-to-medium-duty fleets within Connected Solutions, starting with school buses 1. Fleet vehicles follow predictable schedules. They charge during the day, return to depots by evening, and sit idle overnight when grid demand peaks. Their batteries are also substantially larger than passenger-car packs, making them disproportionately valuable for grid support 2.

What the Pilot Actually Tests

Utilities have always owned their infrastructure: power plants, substations, transmission lines. V2G proposes a model where the utility aggregates assets that consumers already bought and paid for. The Massachusetts pilot asks whether the industry can procure storage from driveways instead of construction sites.