THE STATE’S Energy Facilities Siting Board concluded on Wednesday that it lacks authority to approve large energy storage facilities, which means two projects in Carver and Medway may be in jeopardy.

Energy storage facilities are becoming an integral part of the regional power grid. The facilities help the grid deal with fluctuations in demand by acquiring energy when it is cheaper and more plentiful and releasing it on to the grid when demand is high. They offer a promising way of meeting periods of peak energy demand without building new power plants.

The facilities in Carver and Medway, both of which faced local opposition, were tripped up by a definitional problem. The Energy Facilities Siting Board regulates power generating facilities of 100 megawatts or more. The facilities in Carver and Medway were 250 and 150 megawatts, respectively, but the board ultimately ruled that battery electric storage facilities are storage facilities, not generating facilities.

The board said in its decision that regulating energy storage facilities “would be consistent with the Siting Board’s general statutory mandate.” But the board said state siting statutes were initially approved in 1973 and updated in 1997, before battery electric storage came on the scene.

“The Legislature could have addressed this gap but has not done so to date,” the board said in its decision. “Plainly, if an energy storage system is substituting for a generation asset, it is not considered to be such an asset but a different type of system.”

A group called Save the Pine Barrens led opposition to the projects, calling the one in Carver the third energy project in the community, turning the neighborhood into “an energy sacrifice zone.”

Bryan Betram, legal counsel to Save the Pine Barrens, said lawmakers the decision should  lawmakers should conduct a review of how energy storage facilities are sited. “This decision should spur an important public discussion about how to site and regulate these facilities in a way that balances the Commonwealth’s need to reduce greenhouse gas emissions with the public’s need to ensure these facilities are safely sited and their impacts on communities are minimized and mitigated,” he said.

The Energy Facilities Siting Board, which is chaired by Rebecca Tepper, Gov. Maura Healey’s secretary of energy and environmental affairs, referred the issue to the Department of Public Utilities, which will now have to decide whether to exempt the projects from local zoning laws.

The stakes are high. Both projects, apparently confident they would win approval, successfully bid into the region’s forward capacity market, which pays electricity suppliers to be available three years in the future. The Carver project bid into the market in 2021 and is required to have its power available in 2024 or face a “substantial financial loss.” The company building the facility says oit needs approval to construct the project by June 2023 to meet the deadline.

The Medway project faces a similar situation and must by ready to supply energy by June 1, 2024.