New England’s last running coal-fired power plant, Merrimack Station in Bow, passed an emissions test over the summer that it struggled to complete for more than a year. But only one of its two units that generate electricity completed the test, raising questions about how the plant will operate over the winter and in the years until it’s scheduled to stop burning coal.
As the weather gets colder, the role of Merrimack Station comes into focus for many in the region. The plant in the past has billed itself as something like a security blanket for the electric grid; it is expected to provide power when the region demands more energy than usual resources can provide, like on very cold or very hot days.
The company that owns the plant, Granite Shore Power, has announced they will stop burning coal at Merrimack Station by 2028 and turn the site into a “renewable energy park.” When they announced that transition, the plant said they planned to keep up their obligation to New England’s regional grid operator, ISO New England, to provide “capacity” on the grid.
In exchange for its ability to generate power during times of need, the plant has traditionally received monthly payments funded by ratepayer money to stay online. But from early 2023 until the plant passed its emissions test this summer, state regulators considered operations at the plant to be permit violations.
Now, with only one of its two units having passed an emissions test, the plant still won’t be able to run at full capacity without violating its permit until it passes an additional test. How much power the plant will be able to provide for the grid this winter remains uncertain.
Through a spokesperson, Granite Shore Power declined to answer questions about whether it plans to schedule a retest for the untested unit and questions about whether it has revised its obligations to the grid, saying the company didn’t want to provide commercially sensitive information.
Emissions testing
When Merrimack Station did a routine emissions test in February 2023, it exceeded an emissions limit for particulate matter by about 70%, according to state regulators. Particulate matter is a mix of tiny solids and liquids that can cause health problems if inhaled.
In a statement to NHPR, Granite Shore Power asserted that their failed test had not resulted in “any excessive emissions.” But regulators maintained that any operations at the plant were in violation of its permit until it passed an emissions test.
Merrimack Station made several attempts to retake its emissions test that were canceled due to operational issues, including boiler leaks and electrical breaker issues. In July, the plant tested emissions from just one of its two units, known as MK1 and MK2.
The test measured emissions from MK2, which is about three times the size of MK1. The plant passed the test for MK2, which is now allowed to run. But MK1, which was not operating during the emissions test, is not allowed to generate electricity until it passes a test.
The company is required to update state regulators monthly about their efforts to “diagnose and repair” MK1.
State regulators have given the plant until May 31, 2026 to show that both units can pass an emissions test while running at the same time. If that doesn’t happen, the plant will be required to remove MK1 from its permit and from the facility.
Officials with the Department of Environmental Services declined to comment on whether the agency is pursuing any actions to get MK1 running again.
Providing capacity
Meanwhile, Merrimack Station had been expected to provide power for the grid this winter, after winning obligations during several of the region’s forward capacity auctions. It had the responsibility of providing 438 megawatts of capacity every month between June 2023 and May 2025. (The plant has smaller obligations for kerosene-fired generation as well).
Meeting that capacity obligation would require the plant to run both of their units. With only one having passed an emissions test, it won’t be able to run at full capacity without violating its permits.
For its coal-fired generation, Merrimack Station has been set up to receive payments every month to stay available to run. According to calculations by NHPR based on the capacity of the plant and the clearing price of each forward capacity auction, the Merrimack Station was set to receive $876,000 per month between June 2023 and May 2024, and $1,086,240 per month between June 2024 and May 2025.
The money from those payments is collected, in part, through electric rates. In 2023, for the average ratepayer, charges to support capacity payments came out to around $6 per month.
It remains unclear if Granite Shore Power is still receiving monthly payments and if or when those payments changed.
Power plants are allowed to reduce their obligation or transfer part or all of it to another generator, but those transactions are not made public by the region’s grid operator. If a power plant fails to perform during a time of scarcity on the grid, they can be penalized for the power they aren’t able to provide.
Granite Shore Power declined to comment on whether it had changed its capacity obligation, citing concerns about commercially sensitive information.
Dan Dolan, head of the New England Power Generators Association, said it’s fairly common for power plants to trade or release some of their capacity obligations due to issues with equipment or permitting. Keeping the obligations if a plant cannot meet them would come with downsides, he said – including major penalties that can “far exceed” the capacity payments the facility receives.
The future of coal in New England
The uncertainty around Merrimack Station’s operations has caused some in the region to question why the plant – which plans to transition away from fossil fuels already – is still trying to run at all.
“This whole situation really just feels unfair to ratepayers and to people who are dealing with the pollution of this plant at this point,” said Rebecca Beaulieu, a climate activist with 350 New Hampshire. “I know they said they’re going to stop burning coal by 2028, but they should just abandon ship now. It just seems so wasteful.”
Dolan said the process of closing down a power plant is “painstaking,” and that Granite Shore Power would likely be monitoring the circumstances on the grid to see if they should push their date of retiring coal-fired generation earlier.
“However, the need for peaking facilities in general, whether that's Merrimack or someone else, if anything, is becoming more important in New Hampshire and New England as we continue to electrify broader segments of the economy,” he said.
Jim Andrews, the president of Granite Shore Power, said in a March interview that the plant planned to continue meeting its obligations to provide power to the regional grid through 2026, and may extend their obligations through 2027.
As Merrimack Station transitions away from coal, Andrews said the company intends to continue employing people working at the plant.
