Green Mountain Power has asked Vermont regulators for permission to lift the cap on its popular residential energy storage programs to expand customer access to battery backup power.
GMP’s Powerwall program, in partnership with Tesla, and its Bring Your Own Device battery backup program are capped at 500 new customers per program a year. The Powerwall program is full for 2023, a waitlist for 2024 has maxed out, and 250 customers are on a waitlist for 2025, GMP said in April.
“The unprecedented series of major storms this winter highlights the resiliency and reliability benefits of home energy storage for customers and also the need to remove barriers to pursuing this opportunity for cost-effective backup battery power that is popular with customers, with interest consistently exceeding the cap,” GMP said in its filing with the Vermont Public Utility Commission.
When the storage programs were initially approved in 2020, GMP suggested a 5 MW annual cap, or equivalent to 500 installations a year for each program while monitoring benefits to participating customers and development of the storage market, GMP said.
GMP now says a lengthy waitlist places an unnecessary barrier to participation, and the 5 MW annual cap delays “robust storage deployment and the meaningful benefits it provides, the utility told regulators.
During severe storms, customers in GMP’s home energy programs switch to battery power as the grid is repaired. Home energy storage provided 10,000 hours of backup power for customers in GMP programs this winter, said Mari McClure, GMP’s president and CEO.
About 2,500 customers have more than 4,000 batteries in their homes through GMP programs, the Colchester-based utility said. The batteries are part of the company’s growing network of more than 40 MW of stored energy in home batteries, utility-scale batteries and devices such as car chargers that GMP uses as virtual power plants to reduce the need for costlier power from the New England grid during peak use times such as heatwaves.
This energy-sharing partnership has reduced power costs for customers by up to $3 million a year for the last few years, GMP said.
Through the Powerwall program, customers lease two batteries from GMP for $55 a month or a one-time payment of $5,500. Both save money, GMP said, because customers share energy during peak use times.
In the Bring Your Own Device program, customers purchase a battery from a company they choose and, depending on the amount of energy they choose to share with GMP during peaks, they receive a rebate of up to $10,500.
GMP began offering home batteries to customers in pilot programs in 2017 and was the first utility in the U.S. to partner with Tesla. In 2020, GMP said it became the first utility to win regulatory approval to offer fully tariffed home energy programs for its Powerwall and BYOD pilot programs.