Vermont utility Green Mountain Power (GMP) saved at least US$510,000 during the northern hemisphere’s continuing summer heat wave, using its customers’ Tesla Powerwall batteries to reduce peak electricity demand in what Greentech Media is calling “one of the most robust natural experiments so far to test the efficacy of decentralized energy resources in reducing system-wide stress”.
“This is a game changer,” said Green Mountain President and CEO Mary Powell. “During the heat wave, we were able to leverage these innovations to think differently about managing the energy system affordably, allow our customers to use their cooling systems to stay safe and comfortable, all while lowering the peak, ensuring the stability and safety of the grid, and driving down costs.”
“Now the utility knows exactly how much electricity it would have consumed without the storage, and what system peak capacity charge it would have had to pay,” Greentech notes. “It can compare that to its actual demand and resulting charge.”
Green Mountain Power’s release recounts how customer Mike Wheeler reacted when an app on his smart phone told him his two basement batteries were draining power. “It was so cool!” Wheeler recalled. “I thought, ‘it’s going to grid right now.’”
Wheeler was one of a group of Vermont power consumers who installed a total of 500 Powerwalls under a partnership with the utility. “They provide backup power for his home, like a generator would during an outage,” GMP explains. “But instead of using oil or gas, Powerwalls get their charge by storing energy from either the electrical grid, or from a customer’s solar panels.”
At that particular moment in the July heat wave, the combined effect was like taking 5,000 homes off the grid.
“All those Powerwalls played a big role in cutting carbon and costs for all customers during the heat wave,” the utility reports. “What Mike Wheeler was seeing on his app was GMP sharing access and leveraging the stored energy in those Powerwalls to put back on the grid during those high-use heat wave days. GMP also used energy from larger batteries at its solar facilities in Rutland and Panton to try to ‘beat the peak’—all of that power deploying at one time to reduce demand and cut costs directly for customers.”
“We signed up to have Powerwall battery backup at home so our family can get through occasional outages and not rely on a fossil fuel generator,” Wheeler said. “But knowing our choice to get a Powerwall helped all GMP customers cut costs during the heat wave is a great extra benefit, like you’re doing something for the common good.”