Vermont’s largest energy source is now a virtual power plant

In Vermont, utility Green Mountain Power now runs the state's largest power resource, and it isn't a traditional power plant. It's a "virtual power plant" (VPP), a network of home batteries, large-scale storage, EV chargers, and other resources that the utility can draw on together during times of high demand. During a July heat wave, GMP pulled 90 megawatts from this network, roughly equal to taking 50,000 homes off the grid at peak. Utilities normally have to buy extra power at high prices during heat waves, so avoiding that purchase saved an estimated $6 million for all GMP customers, not just those with batteries. Last year the VPP saved $11 million.

More than 5,000 GMP customers have over 10,000 batteries enrolled, making up 53 of the network's 110 megawatts of total capacity. GMP was the first utility in the country to offer a state-approved battery lease: customers can lease two Tesla Powerwalls for $55 a month, or pay $5,500 upfront for a 10-year lease. In exchange, GMP can tap some of that stored power during peak hours, while the homeowner still keeps backup power during outages. There's also a "bring your own device" option that gives an upfront incentive to customers who buy their own compatible battery.

The payoff extends beyond individual bills. GMP says the growing battery network has already let it permanently retire peaker plants, small power plants that run only during demand spikes and tend to be costly and carbon-heavy, in Vergennes and Rutland, with more retirements planned as the battery network expands. This program is specific to Vermont, so homeowners elsewhere should check what their own utility or state offers.