As energy use on the Island continues to rise, Eversource has made strides in installing two 5-plus mile long electric transmission cables in the seabed between the Vineyard and Falmouth.
Construction on the approximately $310 million project started in December 2023, and is aimed at meeting the growing peak energy demand for the Vineyard.
Eversource, which supplies the Island’s electricity, has finished drilling the trenches in the seafloor for the new cables, officials with the utility said earlier this month. With that work done, the construction sites at Eastville avenue in Oak Bluffs and Mill Road in Tisbury will be cleared in the coming weeks in time for summer.
“The fencing will come down and it will be as it was,” said Stephanie Bete, the project engagement senior specialist with Eversource.
For decades, the Vineyard has been getting its power from four undersea cables. In the summer, those cables get a boost from diesel generators in order to deal with the crush of seasonal visitors.
The infrastructure has shown cracks in recent years, though. In 2021, a cable that was installed in 1986 failed, causing rolling blackouts across the Island.
Given the past issues and growing demand for electricity, Eversource decided to replace one of the existing cables and install a fifth one, both capable of handling 23 kilovolts of power.
The project replaces a past plan to create a large-scale battery storage facility on the Island. That project was scrapped after Island energy and climate experts felt that project would fall short of the Island’s growing electrification needs. When finished, the utility will be able to retire the generators.
A 2024 report from the Martha’s Vineyard Commission found electrical use increased by 17 per cent in the prior 10 years, and that was expected to increase as more people adopt electric heat pumps, induction cooking and electric bikes and vehicles. During that same time period, peak demand rose by 24 per cent.
By 2050, the average household in Massachusetts will use almost three and a half times the amount of electricity on average than it did in 2023, according to Eversource.
To handle these surges, the new cables will have a rated capacity to provide 140 per cent of the predicted usage for the Island in 2050. Eversource has estimated that the increased capacity could make way for 5,000 more residential heat pumps and 24,500 electric vehicles.
“It basically will provide well above the usage needed,” said Ms. Bete. “The Island has seen considerable growth over the last couple decades.”
In the fall, Eversource plans to lay the cable and install about 140 new distribution poles for the project. The new poles will be taller than existing ones in an attempt to keep the wires above the Vineyard’s tree canopy, according to Ms. Bete.
The new cables are expected to go into service in March 2026. The cost of the construction will be shared by customers across eastern Massachusetts and will not appear in bills until the project is complete, according to the utility. The Department of Public Utilities will conduct a review of the project as part of a rate distribution review in the future. The costs will be spread out across the life of the project in order to minimize impacts to customers, an Eversource official said.
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