National Grid Delivers Extra Generators To Nantucket As A Precaution

After last year's undersea cable failure, National Grid is taking no chances.

While Nantucket's electrical system is currently functioning properly, the utility giant took the precautionary measure of delivering numerous roll-off generators to the island on Monday. The large Aggreko units have been set up at National Grid's property on Candle Street in downtown Nantucket, close to the lot used for valet parking. 

“Out of an abundance of caution, we are proactively positioning additional generation assets on the island to ensure continued reliability," said Brendan Moss, National Grid's director of strategic communications and corporate affairs in New England. "National Grid’s electric system is operating normally, and the generator units will be available throughout the summer if needed.”

Following the failure of one of the island's two undersea electric cables in May 2024, which lasted for nearly two weeks, National Grid made a similar move to bring 11 generators to Nantucket to ensure that electrical service was maintained for the island.

The utility provider's existing electrical backup system for Nantucket includes a 6-megawatt / 48-megawatt-hour lithium-ion Tesla system, along with a 15-megawatt generator and power control house at National Grid’s three-acre property east of Nantucket Memorial Airport.

The company believes that the existing undersea cables and the backup system are sufficient to meet Nantucket's forecasted peak demand. However, the additional generators were delivered this week in case of an unexpected incident or situation, such as adverse weather conditions, transportation issues, or sudden load changes. 

The island’s first 28-mile extension cord to the mainland was installed beneath Nantucket Sound back in 1996 when the island’s peak electricity usage was just 20 megawatts. The undersea cable installed by National Grid that year ran from Nantucket to Harwich on Cape Cod with a capacity of 36 megawatts. It brought to an end the era in which the island generated its own electricity at the former downtown Nantucket Electric Company power plant along the waterfront that featured six massive diesel generators.

As Nantucket’s electricity usage continued to grow, a second undersea cable was installed in 2006 to meet the demand. This one connected the island’s substation on Candle Street to Kalmus Beach in Hyannis. The $41 million, 38-megawatt cable was paid for through a National Grid surcharge on Nantucket electric bills.

In 2019, National Grid installed the Tesla battery storage units and the 15-megawatt generator on the island, replacing Nantucket’s previous backup power source: two aging 6-megawatt diesel generators. At the time, the battery installation was the largest of its kind in the Northeast.