Energy Storage

GMP offers customers batteries that double as meters

Green Mountain Power in Vermont has embarked on a program that will allow some of its customers to combine a home backup battery system with the functions of an advanced meter.

For customers, the battery-plus-meter system provides backup power during an outage and more visibility and control over their electricity usage. For the utility, the system provides more granular customer data and is another step in Green Mountain Power’s transformation.

“We are moving to a distributed system” and that requires more batteries, Josh Castonguay, vice president and chief innovation officer at Green Mountain Power, said.

The Tesla Powerwall, like most battery systems, already comes with a metering system. “That was the ‘ah ha’ moment,” Castonguay said. “It became clear we could leverage the batteries and take it a step further,” he said.

The missing piece was the software that allows the onboard battery meter to communicate with the utility’s metering and billing systems. During the Resilient Home pilot program, existing meters will remain in place and be used to check and verify the data from the battery-meter system. Green Mountain Power has applied for a patent for the software that allows the battery meter to communicate with the utility’s billing system. “Once we ramp this up, we will have the ability to use more battery systems,” Castonguay said.

“Storage devices, like the Powerwall, have already proven incredibly useful in allowing us to manage the entire grid more effectively when you’re considering carbon and cost,” Castonguay said.

One of the reasons the utility is able to offer incentives that make it cheaper for customers to purchase batteries is because Green Mountain Power uses the batteries to reduce the amount of power it needs to buy during times of peak power demand.

Last summer, the utility’s network of stored energy saved customers more than $500,000 in a single day when Green Mountain Power used that shared power to drive down demand on the grid during the annual New England peak. Not counting other storage sources, such as electric vehicles, Green Mountain Power’s original Powerwall program accounted for $380,000 of those savings.

Based on that experience, Castonguay says the Resilient Home program has the potential to save all Green Mountain Power customers $1.5 million over the 10-year life of the pilot program. The utility estimates its original Powerwall program will save customers more than $2 million.

The original Powerwall program ended up being fully subscribed last fall with 2,000 batteries deployed.

“There has been tremendous interest in the Resilient Home program so far, with more than 1,000 customers reaching out in the first day of the program,” Green Mountain Power spokeswoman Kristen Kelly said.

Green Mountain Power serves approximately 265,000 residential and business customers in Vermont.

Association offers BTM storage resource

The American Public Power Association has produced a report that outlines the values and challenges of behind the meter energy storage systems, from both the customer and utility point of view.

The report focuses on lithium-ion battery storage because that is the predominant BTM energy storage technology. This report also includes highlights of recent federal and state activities, and utility case studies.