||| FROM THE NANTUCKET INQUIRER & MIRROR |||
Orcas and Nantucket Islands are each roughly the same size and the same distance off their respective coasts. We share the same concerns about the high cost of living, lack of affordable housing, tourist management, ferry problems and environmental degradation. We are living on opposite ends of the country but many of the issues and opportunities are the same. Recently theOrcasonian and the Nantucket Inquirer and Mirror decided to share articles of mutual interest with our readers.
Nantucket’s electricity demand is growing so fast that the island may need a third undersea power cable more than a decade earlier than previously expected – raising concerns about reliability, cost and long-term infrastructure planning.
The revelation came in a letter from town counsel Devan Braun to the state’s Grid Modernization Advisory Council April 3 and released Tuesday by the town.
“A failure of one of the two undersea cables during the peak season would leave the island without sufficient capacity to power essential services, posing a significant risk of prolonged outages and widespread disruption,” she wrote.
“Recent failures also underscore the vulnerability of current infrastructure, particularly during peak periods, making greater urgency and transparency essential.”
In 2018, estimates projected that a third cable wouldn’t be needed until 2044. Recent communications with National Grid, however, suggest the timeline has accelerated, and a third cable could now be required as early as 2033. The island’s energy use is growing five times faster than the state average.
A third cable, estimated to cost more than $200 million, would impose a significant burden on Nantucket ratepayers if it follows the same cost structure as the first two.
Island residents already finance the existing cables through a roughly 15 percent cable facility surcharge.
The town is asking the advisory council to explore funding opportunities through federal and state programs.
Braun also asked for greater transparency from National Grid and state agencies about contingency measures and whether there are plans to replace the island’s first undersea cable, which is nearing 30 years of service, with a higher-capacity line as part of long-term infrastructure upgrades.
In 2024, the island experienced two major electric service disruptions: an undersea cable failure in May and a widespread downtown outage during the December Christmas Stroll weekend.
The May incident, caused by a faulty current that triggered an automatic shutdown, did not interrupt service due to backup systems and the second cable.
But it left the island in a vulnerable state for nearly a week while the cable was repaired. Had the outage extended into the summer, Braun warned, the consequences could have been much more severe.
In December, nearly 200 downtown businesses lost power for 27 hours during the Christmas Stroll, resulting in an estimated $8 million in lost revenue. National Grid attributed that outage to two underground cable failures and said it was unrelated to the undersea transmission system.
The island also faces a “reverse capacity limit,” Braun said, which restricts the amount of renewable energy that can be generated locally without the risk of power being “back-fed” to the mainland.
The town is asking for upgrades at its Candle Street substation to address the issue and “unlock Nantucket’s renewable energy potential.”
The island’s typical energy use ranges from 15 to 20 megawatts per day most of the year, but can spike to over 50 megawatts during the summer peak season. Nantucket recorded its highest-ever one-day load, 55 megawatts, on Aug. 8, 2022.
National Grid installed the island’s first undersea cable in 1996, a 36-megawatt line connecting Nantucket to Harwich at a cost of $30 million. A second, 38-megawatt cable to Hyannis followed in 2006 at a cost of $41 million.
Prior to 1996, all of Nantucket’s electricity was generated on-island using steam and later diesel generators.
In 2019, National Grid installed a Tesla lithium-ion energy storage battery system alongside a 10-megawatt turbine generator and power control house on property near Nantucket Memorial Airport. The $81 million project was designed to delay the need for a third undersea cable and address isolated power outages. Unlike the undersea cables, the cost of that project was spread across all National Grid ratepayers, not just those on Nantucket.
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