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New England grid operator says small-scale solar is driving down electricity demand on some days

Power lines
Dan Tuohy
Power utility lines

As long as there’s been electricity, humans have used more of it in the middle of the day, according to Matt Kakley, a representative from ISO-New England, the organization that runs New England’s regional grid. But things are changing with small-scale solar.

“What we’ve seen is that that’s still true, but over time, as more and more people have put solar panels on their roofs or of their homes or their businesses, is that they're getting that electricity from those solar panels rather than the bulk power system,” he said.

That means on some days, when the weather conditions are right, the demand on the regional power system is lower in the middle of the day than it is in the middle of the night. Those are called “duck curve” days, because the demand curve looks like a duck.

ISO-New England saw more duck curve days in 2022 than in all other years, combined – 45, in total.

“We saw them on weekdays; we saw them on weekends. We saw them pretty much every month of the year with a couple of exceptions, and really this has started happening more and more than we've ever seen in New England before,” Kakley said.

Kakley says understanding duck curves is important to plan for the grid of the future. It’s one way New England residents can see the clean energy transition play out in real time.

“Things that were true and taken as facts 15, 20 years ago are changed now,” he said. “The clean energy transition is happening. It’s already happening and will continue.”

When less electricity is needed from the regional grid, big power plants that run on fossil fuels – and emit the greenhouse gases that drive climate change – are less needed.

The grid operator incorporated better modeling for small-scale solar into its daily forecast for operations in 2019. Kakley says it’s always important for the ISO to have an accurate weather forecast, but even more so as the impact of solar panels increases.

In 2021, New England had about 4,800 megawatts of solar. By 2031, that’s expected to more than double to 11,500 megawatts, with the majority of that being the smaller-scale panels that drive duck curve days.

Mara Hoplamazian reports on climate change, energy, and the environment for NHPR.