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.
ISO says the maximum amount of solar energy in New England — from rooftop panels and commercial solar farms, which connect to the grid — is expected to nearly double in the next 10 years. The grid operator anticipates capacity to grow to 13,466 MW in 2033 from 7,345 MW this year and it includes a doubling in behind-the-meter solar capacity, to 8,000 MW.
TOPPING SHEDS WITH SOLAR PANELS
Matt Wagner is helping push demand for solar power. He’s the owner of Upright Energy, which installs solar panels on sheds built in Unity by Amish workers. “It seems like it’s kind of more and more all the time,” he said.
The buildings, which are typically 24 feet or 32 feet in length, are used for home offices or an extra room.
Wagner said he stopped installing solar panels on sites four or five years ago and instead opted to deliver them already attached to pre-built sheds, costing $7,000 or more.
“Instead of driving all over the state, we build in the shop and deliver as a completed project,” he said.
Sam Monaco, owner of Monaco Studios in Falmouth, had solar panels installed three years ago as part of a home project that included installation of heat pumps to increase zero-carbon energy use.
“A lot of musicians really love to come to our studio and make a solar-powered record,” he said.
The solar panels allow him to earn bill credits during months when heating from the pumps is modest. He pays for electricity beginning in December when temperatures drop, and said he spends the same or less for electricity than before he revamped his heating and electricity.
Power produced at his house goes to the grid, and he deducts what he’d pay for electricity. “We’ve never made enough to produce a surplus to sell back to CMP,” Monaco said.
Rooftop solar in Central Maine Power’s service territory rose nearly 50% since last year, to 27 megawatts from 18.1, according to spokesman Jon Breed. The number of solar projects jumped to 3,913 from 3,048.
WHAT HAPPENS WHEN THE SUN GOES DOWN?
In Versant Power’s territory, which includes Maine’s most rural and sparsely populated northern counties, some solar farms produce power connected to a distribution system rather than the grid, making it comparable to rooftop solar, said spokeswoman Judy Long.
Versant this year added 4.7 MW of smaller solar projects of up to 25 kilowatts each, including rooftop solar, she said. A total of 589 projects went into service year, she said.
The typical electricity cycle is low use in the morning, peaking at lunchtime and again at elevated levels between 4 and 8 p.m., she said. The sun sets as demand for electricity rises, requiring Versant to bring in power generated by other sources, such as hydro and natural gas, to make up for diminishing solar power, Long said.
Versant is sharing with CMP a $65 million federal grant for “smart grid” technology to more quickly connect solar panels and wind turbines to its electricity systems.
Mike Knowland, manager of forecasting and scheduling at ISO, said the number of “duck curve” days has increased steadily since 2018 when it was first recorded, on a weekend. It’s risen from 73 such days last year and 45 in 2022.
“Every megawatt-hour from solar, every MWh from wind is a MWh you don’t have to get from somewhere else,” he said.
That “somewhere else” is likely natural gas, a fossil fuel that accounted for 55% of power generation in New England in January, according to ISO. Solar power, in contrast, accounted for 4% of generation and does not reflect behind-the-meter solar, but are instead larger solar installations such as solar farms that are part of the region’s energy markets or provide data to ISO.
Steve Hinchman, senior counsel at ReVision Energy, which installs solar panels, heat pumps, battery storage and equips solar farms, said the “number of projects and volume continue to grow year after year.”
But he said an ISO report earlier this year projecting a 17% spike in electricity consumption in the next decade is more shocking than the rising use of rooftop solar. Energy use in New England grew steadily each year between 1995 and 2005, driven primarily by strong economic growth and air conditioning, ISO said. But since 2005, annual energy use has fallen due mainly to improved energy efficiency in cooling and heating, energy-efficient appliances and lighting and more power generation from rooftop solar, the grid operator said.
It now predicts steady growth in energy use as state policy goals for carbon emissions reductions drive an increased electrification of heating systems and transportation.
“It’s going to challenge our region. That’s a lot of new energy,” Hinchman said.
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