NANTUCKET, Mass. — National Grid on Tuesday unveiled the largest battery storage project in the Northeast, with hopes that the project can help make Nantucket’s electric supply system more reliable and resilient.

The utility installed a 6 megawatt/48 megawatt-hour lithium-ion battery energy storage system that will work alongside a new 15 megawatt generator and power control house on the island.

Two undersea cables supply electricity to Nantucket, which is 30 miles offshore.

Should anything go wrong, the island has relied on two 6 MW diesel generators for backup power. The generators had reached the end of their lifespan and needed to be replaced.

“We face a serious risk if one of those cables goes down,” Nantucket Town Administrator Libby Gibson said. “If one goes down it is not enough to keep us going.”

The new battery energy storage system, built by Tesla, and the new generator have the capacity to supply the island with energy during its peak summer months should one of the cables experiences an outage, according to National Grid.

The demand for electricity on Nantucket has grown in the past 10 years, from 37 MW in 2008 to nearly 49 MW in 2018, according to National Grid.

This project, which cost about $81 million, is seen as a way to help stave off the massive undertaking of installing a third undersea cable.

Eversource also is working on battery energy storage projects on Martha’s Vineyard and in Provincetown on Cape Cod.

Lauren Sinatra, Nantucket’s energy coordinator, said she was pleased with the National Grid project.

“The town of Nantucket commends National Grid’s decision to deploy an innovative energy storage solution on the island,” she said. “We are confident that this innovative hybrid project, combined with targeted energy savings programs, will play a transformational role in meeting Nantucket’s near- and long-term energy needs and sustainability goals.”