Vermont PUC lifts caps on Green Mountain Power battery storage programs with Tesla, others

Demand for GMP’s Tesla-based and “bring your own device” energy storage programs has outstripped annual caps amid winter storms and summer floods.

With demand outstripping program caps, the Vermont Public Utility Commission earlier this month approved an expansion of Green Mountain Power’s residential storage programs, including one that uses Tesla battery systems.

The PUC on Aug. 17 approved lifting a 5-MW annual cap and updated installation and equipment costs for GMP’s Energy Storage System, or ESS, and Bring Your Own Device, or BYOD, battery-storage programs. They were first approved in 2020.

GMP in April asked the PUC to lift the program caps following a series of severe winter storms. Vermont was also hit with devastating flooding in mid-July.

About 2,500 customers have signed up for the ESS program, which totals about 22 MW, according to the PUC’s decision. Under the program, customers lease for 10 years two Tesla Energy Storage 2 systems with integrated inverter units and one Tesla Gateway. A waitlist for the program exceeds 1,000 customers, which is more than could have been accomodated under the caps.

Nearly 200 customers are enrolled in the BYOD program, and GMP expects 100 customers will enroll over the rest of this year, according to the PUC decision.

“Recent storm events throughout GMP’s service territory, which have led to widespread outage events over the past year, are also likely to continue to place upward pressure on that demand,” the PUC said.

When electricity demand peaks, GMP networks the residential battery capacity, along with utility-scale batteries and car chargers, into a virtual power plant of about 50 MW, according to the utility. The VPP has saved GMP customers up to $3 million a year for the last few years, the utility said.

The PUC approved increasing the ESS program lease cost for each customer to $22,000 from $16,300 to reflect inflationary pressures and increased installation costs. GMP will be able to keep its monthly $55 lease payment unchanged because the federal Inflation Reduction Act provides a 30% investment tax credit for the systems used in the program.

Under the BYOD program, customers buy and install their own energy storage systems and enroll them in GMP’s Energy Management Platform. The customer receives upfront incentive credits ranging from $850/kW to $1,050/ kW for allowing GMP to manage the customer’s energy storage system during peak events for three- or four-hour periods, the PUC said in its decision. The incentive credits remain unchanged under the PUC’s decision.

GMP expects lifting the cap on the programs and adjusting ESS program’s fees will produce financial benefits for all its customers.

The utility estimates individual ESS systems will produce a positive lifetime net-present value of $2,749 through revenue from customer payments, reduced forward capacity market and “regional network service” obligations, energy savings, and renewable energy standard benefits.

Assuming 600 ESS program systems are installed annually, GMP expects a lifetime net-present value of $4.9 million for the systems installed over the next three years, the PUC said. The utility expects its BYOD program will produce $1.1 million in value in the next three years.

The battery storage programs are authorized to run through September 2026.

GMP provides its more than 270,000 customers with carbon-free electricity that is 78% renewable on an annual basis, according to the Colchester, Vermont-based utility.