As president and CEO of Green Mountain Power in Vermont, Mary Powell developed the first utility partnership with Tesla to attach residential Powerwall batteries to the grid, providing backup clean power for the utility when needed. Customers could earn money by essentially filling the batteries at night and dispatching them during the day, Powell explained in a 2016 interview with Vxartnews.
Today, such arrangements are increasingly promoted by clean energy advocates, who’ve dubbed distributed grid-connected batteries — plus solar — “virtual power plants” that allow homeowners and businesses to help out utilities during times of high demand. They’re also central to Powell’s current mission as head of the nation’s largest residential solar company.
Powell left Green Mountain in 2019 after two decades with the company, and in 2021 she became CEO of Sunrun. In an interview during a recent conference near Chicago, she spoke about how the culture of her former industry can slow the pace of innovation that’s much needed to address climate, cost and reliability concerns.
“You're talking about a 100-plus-year-old system and way of thinking, and you compound that with the fact that utilities’ whole culture is built for ‘slow and no’ and ‘protect, preserve, defend.’ For so many years, it’s been a one-way system,” Powell said.
Virtual power plants are a prime example of the coming change. Powell said utilities’ experience with energy efficiency in recent decades provides a look at what might be coming for such pairings of solar and storage.
“I would say energy efficiency was the disruption — the first opportunity for utilities to start to think differently about their role and their mandate. And as we know, that took like 20 years, even for the most progressive utilities, to embrace.”
Utilities can generally choose to incorporate virtual power plants into their rate structures and grid services, and state regulators and legislatures can facilitate the concept through decisions, laws and policies that create incentives and provide standards. The Illinois legislature is considering a bill that would essentially allow the agency that procures power on behalf of utilities to contract with virtual power plants.
Green Mountain Power was an early adopter of energy storage under Powell’s leadership, and broader adoption of the technology is ramping up quickly. The U.S. Department of Energy noted in a 2023 report that, “deploying 80-160 GW of virtual power plants (VPPs) — tripling current scale — by 2030 could support rapid electrification while redirecting grid spending from peaker plants to participants and reducing overall grid costs.”
That means utilities will have to adapt quickly, and Powell sees a significant role for private developers in that transition. Powell describes Sunrun as a “clean energy lifestyle company,” branching into technologies like smart electric panels and EV charging.
“When you think about customers having heat pumps, when you think about them having electric vehicles, you make sure that you're leveraging all of that in a way that's beneficial for the grid and beneficial for the customer.”
That focus on the end users of electricity is in part a bet that utilities’ need for solar power will eventually catch up to consumer demand.
“When I went to Sunrun I said to the team, ‘We’ve got to stop wandering around trying to convince every Tom, Dick and Harry utility to utilize our resources.’ We’re doing it, we just need to scale as fast as we can.
“Because guess what, utilities are going to hit the wall, they are hitting the wall in some parts of the country, and they don't have the ability to meet the kind of capacity demands that are projected over the next five years. They're going to need our resources.”
Despite that expected market demand, Powell said legislative and regulatory bodies also have a role to “nudge utilities in the right direction.” Illinois in particular, she said, provides a strong example.
“Illinois has done an amazing job. Making sure that rooftop solar is considered as part of the RPS [Renewable Portfolio Standard] is really thoughtful policy. And I am encouraged with a lot of the conversations about how we could leverage storage more. So yeah, we're very bullish about Illinois.”
Powell also said she has no regrets about leaving the utility sector to work at Sunrun.
“Frankly, even the fastest-moving utility was moving a little too slow for me. We weren't scaling as fast as I would have loved us to be able to scale. It's awesome to work on mission-driven work that you feel is valuable for the people you serve and for the planet at the same time.”