In the sweltering heat of July, when air conditioners across Vermont were running at full tilt, a unique solution stepped in to stabilize the power grid. Instead of relying on traditional fossil fuel plants, Green Mountain Power (GMP) tapped into a virtual power plant (VPP)—a network of distributed batteries and energy storage systems. This innovative approach not only met the peak demand but also saved customers approximately $6 million in just one peak hour.
The VPP, which now boasts a capacity of 110 MW is a testament to the power of decentralized energy. Comprising over 10,000 batteries in more than 5,000 homes this digital grid is transforming how energy is managed and consumed. For those considering electric vehicles (EVs) or home solar systems, Vermont’s model demonstrates how individual energy storage can collectively support the broader grid.
Vermont’s Virtual Power Plant: A Game Changer
GMP’s VPP is now the largest single energy source in Vermont, with a capacity of 110 MW. During the July heatwave, it dispatched 90 MW to meet the peak demand, effectively taking the equivalent of 50,000 homes off the grid. This strategic move prevented the need for more expensive and environmentally harmful peaker plants, which are typically used during high-demand periods.
The success of the VPP has led to significant cost savings for customers. In just one peak hour, the VPP saved an estimated $6 million building on the $11 million saved the previous year. This achievement has also allowed GMP to permanently close two peaker plants in Vergennes and Rutland further reducing reliance on fossil fuels and lowering carbon emissions.
During the summer months, the VPP can cover nearly 10% of Vermont’s peak electricity demand making it a crucial component of the state’s energy strategy. The VPP’s ability to quickly respond to grid needs has made it an indispensable tool for maintaining grid stability and reducing energy costs.
How the Virtual Power Plant Works
The VPP operates by connecting thousands of energy resources—including residential batteries, utility-scale storage, EV chargers, and hydroelectric plants—into a single, coordinated system. GMP’s VPP is unique because more than half of its capacity, 53 MW comes from residential energy storage systems. These batteries, installed in homes across Vermont, can be remotely controlled to release stored energy during peak demand periods.
This centralized management allows GMP to modulate the charge and discharge of batteries in response to real-time grid conditions. When a peak in demand is anticipated, the VPP’s software commands the batteries to release their stored energy, thereby reducing the This coordinated effort ensures that the VPP functions as a scalable resource, comparable to a traditional power plant but with the added benefits of being distributed and closer to the point of use.
Batteries and EV Chargers: The Backbone of the VPP
GMP has been a pioneer in promoting residential energy storage, offering a state-approved lease program for home batteries. Customers can lease two Tesla Powerwall batteries for a monthly fee or pay an upfront cost, with the understanding that GMP can access a portion of the stored energy during peak times. This mutually beneficial arrangement provides homeowners with backup power during outages while also contributing to the stability of the grid.
The VPP also includes EV chargers, which can be modulated to reduce energy consumption during peak hours. This integration of EV chargers into the VPP is a step towards a more sustainable and efficient energy ecosystem. In the future, GMP envisions a system where EVs can participate in vehicle-to-grid (V2G) or vehicle-to-home (V2H) programs, further enhancing the flexibility and resilience of the grid.
As the VPP continues to grow, GMP plans to retire more peaker plants, further reducing the state’s reliance on fossil fuels. This shift towards cleaner, more efficient energy storage solutions is not only beneficial for the environment but also for the wallets of Vermont’s residents.
