Solar power is cutting daytime electricity demand on New England’s grid

Jan. 3—For the first time, there were over 100 days in 2024 when customers used more electricity from the region’s grid at night — when most people are asleep — than during the day. Before 2018, there wasn’t a single day when this happened.

The trend reflects that many people are powering their homes and businesses with electricity generated by rooftop solar panels instead of drawing from the grid, which is fueled by power plants that typically burn natural gas.

Maine accounts for a small part of rooftop solar power in the region, but the state saw a sharp increase in the electricity generated by these panels over the last year.

Installing rooftop panels doesn’t necessarily bypass utilities like Central Maine Power Co. and Versant Power. If the panels generate more electricity than a home needs, utilities can purchase the excess and distribute it to others.

Rooftop solar is known as “behind the meter” because it does not take power from the regional grid. That is why, on days when rooftop solar use is high, it creates a dip in daytime energy demand on the grid instead of the typical lunchtime spike. The pattern is called a “duck curve” because, when represented as a line graph, it resembles the profile of a waterfowl, said ISO-New England, the region’s grid operator.

ISO said it’s most common during weekends in the spring, but it can happen whenever the sun is out and temperatures are relatively mild. If New Englanders aren’t using much electricity for heating or cooling, grid demand can drop significantly.

The trend is unlikely to affect retail electricity prices on a customer’s power bill, ISO said. But that could change if time-of-use rates become more popular. State regulators are considering making those rates, which increase when demand on the grid is high, more widespread in Maine.

Power from rooftop solar panels in New England accounted for an estimated 5,443-gigawatt hours this year, up 27% from 2023. Maine generated less than a tenth of that, 405 GWh, but it increased the most, up nearly 95% from 2023. Connecticut and Massachusetts, New England’s largest states with the most cities and suburbs, generated the greatest estimated amount, at 3,876 GWh, up about 20% and 27% respectively.

A GWh is equivalent to 1 million kilowatt-hours, and a power plant with a capacity of 1 gigawatt can power 876,000 homes for one year, according to Carbon Collective, an energy investment adviser.

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