Green Mountain Power’s virtual power plant — an aggregated network of home batteries, EV chargers, hydro sites and utility-scale storage — dispatched 90 MW during an early-July Vermont heat wave, avoiding about $6 million in peak electricity costs. The system has grown to roughly 110 MW of capacity (53 MW from residential batteries), with over 5,000 customers and more than 10,000 batteries enrolled. The storage fleet can meet nearly 10% of Vermont’s summer peak, has helped retire peaker units, and offers lease and BYOD options that preserve backup power for participants.
Vermont’s Virtual Power Plant Delivered 90 MW During July Heat Wave, Saving Customers $6M
Photo Credit: Green Mountain Power
As an early July heat wave drove up air-conditioning use across Vermont, Green Mountain Power (GMP) said the state’s largest power resource was not a conventional generating station but a virtual power plant made up of home batteries, EV chargers, hydro facilities and larger storage systems working in concert. GMP says this coordinated fleet avoided an estimated $6 million in peak electricity costs during the event.
How the Virtual Power Plant Worked
According to Electrek, GMP dispatched about 90 megawatts from its virtual power plant at the moment of highest demand — roughly the equivalent of taking some 50,000 homes offline at peak. By using stored electricity during expensive wholesale-price windows instead of buying power on the market, GMP reduced costs that would otherwise have been passed on to all customers, including those without batteries.
Scale and Composition
The network has expanded to about 110 MW of coordinated capacity, making it Vermont’s single largest power resource. Residential battery systems provide 53 MW — more than half the total. More than 5,000 customers have enrolled, contributing over 10,000 batteries, and the aggregated resource also taps utility-scale batteries, commercial buildings, EV chargers and hydroelectric sites.
Grid Benefits and Local Impacts
Because stored power is located close to where people live, the grid can draw on it during extreme weather instead of relying solely on costly market purchases. That reduces system strain during dangerous heat when blackouts and price spikes are more likely, while participants retain backup power for outages.
GMP reports the batteries in its virtual power plant can meet nearly 10% of Vermont’s summer peak demand, giving the state the highest storage-to-peak ratio in New England. Flexible capacity at this scale has already enabled the permanent retirement of peaker units in Vergennes and Rutland, lowering local emissions and operating costs.
How Customers Join
GMP has expanded enrollment by making batteries more accessible. The utility was the first in the U.S. to offer a state-approved, tariff-based lease for home batteries, allowing households to obtain backup power without paying the full upfront cost. Customers can lease two Powerwalls for $55 per month or pay $5,500 upfront for a 10-year lease; in return, GMP may use a portion of stored electricity during demand spikes while participants retain backup capacity for outages.
Customers who prefer to buy their own compatible battery can join GMP’s Bring Your Own Device (BYOD) program and receive an upfront incentive while helping turn thousands of separate home systems into one coordinated grid resource.
“It is reassuring and keeps us comfortable at home, and we also love how the program is reducing power costs for all GMP customers, too,” said GMP customer Pollyanna Bladyka.
Takeaway
GMP’s virtual power plant demonstrates how distributed storage and smart coordination can reduce peak costs, improve resilience for participating households, and lower emissions and operating needs for fossil-fuel peaker plants. The program’s combination of customer incentives, lease options and BYOD flexibility helped scale the resource to meaningful system impact.
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