Dispatching 90 Megawatts During Heatwave Saves $6 Million in Electricity Costs
In early July of this year, Vermont experienced a severe heatwave, with temperatures soaring above 90 degrees Fahrenheit, driving a surge in electricity demand. Local utility Green Mountain Power (GMP) activated its virtual power plant (VPP) and dispatched 90 megawatts (MW) of power during peak hours, saving an estimated $6 million in electricity costs for all customers. GMP stated that this dispatch was equivalent to reducing the electricity demand of 50,000 households during the peak period, effectively lowering the cost of purchasing electricity when wholesale prices spiked.
GMP’s CEO noted that the virtual power plant, through distributed energy storage systems, provides stable power during periods of maximum grid stress, not only alleviating peak loads but also significantly reducing electricity costs for customers. This system has become a cornerstone of Vermont’s energy transition.
110 Megawatts Capacity Becomes State’s Largest Power Source
By the end of July, GMP’s virtual power plant had reached a total capacity of 110 megawatts, officially surpassing traditional power plants to become Vermont’s largest single power source by capacity. Of this, 53 megawatts come from residential Tesla Powerwall battery systems, with the remainder including utility-scale batteries, electric vehicle chargers, and dispatchable commercial electricity equipment. GMP stated that these energy storage systems can now meet nearly 10% of the state’s summer peak electricity demand, giving Vermont the highest storage-to-state-peak ratio in New England.
The rapid growth of GMP’s virtual power plant has been driven by increasing customer participation. As of July, over 5,000 customers had joined the program, contributing more than 10,000 batteries. During peak grid periods, GMP can remotely dispatch this distributed stored power while ensuring that customers retain at least 20% to 30% of backup power to mitigate outage risks. Participating customer Pollyanna Bladyka shared that her home batteries continued to supply power during a storm, keeping her household running normally while also helping to reduce electricity costs for all customers.
Residential Battery Leasing Program Lowers Barriers to Participation
To promote the adoption of energy storage, GMP launched the first state-approved residential battery leasing program in the U.S. Customers can choose to lease two Tesla Powerwall batteries for $55 per month or pay $5,500 upfront for a 10-year lease. During the lease period, GMP can dispatch a portion of the stored power during peak hours as compensation for customers participating in the virtual power plant. Additionally, GMP offers a “bring-your-own-device” option, encouraging customers to purchase compatible batteries and providing upfront incentives.
GMP stated that the successful operation of the virtual power plant has led to the permanent closure of two peaker plants in Vergennes and Rutland. These plants, typically activated during surges in electricity demand, are costly to operate and have high carbon emissions. As the battery network continues to expand, GMP plans to phase out more peaker plants, further reducing the grid’s carbon footprint.
GMP noted that the virtual power plant saved customers approximately $11 million in electricity costs last year and played a critical role again during the early July heatwave. With customer participation continuing to grow, the virtual power plant not only enhances grid resilience but also sets a model for Vermont’s clean energy transition. Experts believe this approach could serve as a reference for other states looking to develop distributed energy storage systems.
