Behind-the-meter solar panels and a growing network of batteries helped prevent blackouts and saved consumers millions of dollars.
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On June 24, as temperatures in the Northeast hit their
highest levels so far this year, demand on the New England grid approached
maximum capacity, climbing even higher than forecast. Then, unexpected outages
at power plants reduced available generation by more than 1 gigawatt.
As pressure increased, grid operator ISO New England made sure the
power kept flowing by reducing exports to other regions, arranging for imports
from neighboring areas, and tapping into reserve resources.
At the same time, rooftop and other “behind-the-meter” solar panels throughout the region, plus Vermont’s network of thousands of batteries, supplied several gigawatts
of needed power, reducing demand on an already-strained system and saving
customers millions of dollars. It was a demonstration,
supporters say, of the way clean energy and battery storage can make the grid
less carbon-intensive and more resilient, adaptable, and affordable as climate
change drives increased extreme weather events.
“As we see more extremes, the region still will need to
pursue an even more robust and diverse fleet of clean energy resources,”
Dickerson said. “The power grid was not built for climate change.”
On June 24, behind-the-meter solar made up as much
as 22 percent of the power being used in New England at any given time,
according to the Acadia Center. At 3:40 p.m., total demand peaked
at 28.5 GW, of which 4.4 GW was met by solar installed
by homeowners, businesses, and other institutions.
As wholesale power prices surpassed $1,000 per
megawatt-hour, this avoided consumption from the grid saved consumers at least
$8.2 million, according to the Acadia Center.
This estimate, however, is conservative, Dickerson said. He and his colleagues also did a more rigorous analysis accounting for the fact that solar suppresses wholesale energy prices by reducing overall demand on the system. By these calculations, the true savings for consumers actually topped $19 million, and even that seems low, Dickerson said.
In Vermont, the state’s largest utility also relieved some
of the pressure on the grid by deploying its widespread network of residential
and EV batteries. That could save its customers some $3 million
by eliminating the utility’s need to buy expensive power from the grid and
reducing fees tied to peak demand.
“Green Mountain Power has proven that by making these
upfront investments in batteries, you can save ratepayers money,” said Peter
Sterling, executive director of trade association Renewable Energy
Vermont. “It’s something I think
is replicable by other utilities in the country.”
Green Mountain Power’s system of thousands of batteries is
what is often called a “virtual
power plant” — a collection of geographically distributed resources
like residential batteries, electric vehicles, solar panels, and wind turbines
that can work together to supply power to the grid and or reduce demand. In
Vermont, Green Mountain Power’s virtual power plant is its largest dispatchable
resource, spokesperson Kristin Carlson said. The 72-MW system
includes batteries from 5,000 customers, electric school bus
batteries, and a mobile, utility-scale battery on wheels.
The network began in 2015 with the construction of
a 3.4-megawatt-hour storage facility at a solar field in Rutland,
Vermont. Two years later, the utility launched a modest pilot program
offering Tesla’s Powerwall batteries to 20 customers, followed
in 2018 by a pilot that paid customers to share their battery
capacity during high-demand times. In 2022, a partnership with South
Burlington’s school district linked electric school buses to the system, and
in 2023, state regulators lifted an annual cap on new enrollments it had
imposed on a Green Mountain Power program that leases batteries to
households. The number of customers with home batteries has since grown
by 72%.
“We’ve had a really dramatic expansion,” Carlson
said. “It is growing by leaps and bounds.”
The network saved consumers money during the heat wave by
avoiding the need to buy power at the high prices the market reached that day,
but also by helping to lower the “capacity fees” charged by ISO New England. These charges are
determined by the one hour of highest demand on the grid all year, and then
allocated to each utility based on their contributions to that peak. By pulling
power from batteries rather than just the grid, Green Mountain Power lowered
its part of the peak.
If the afternoon of June 24 remains the time of
peak demand for 2025, Green Mountain Power’s 275,000 customers
will save about $3 million in total and avoided power purchases, the
utility calculated. Looking ahead, more hot weather and further expansion of
the utility’s virtual power plant will likely continue to put money back in
customers’ pockets, Sterling said: “When you play that out over many years, that’s real savings to ratepayers.”
This story was originally published by Canary Media.
