Utility-owned large scale battery energy storage

Here you will find information about the electric companies’ pending and approved battery energy storage systems (BESS). The electric companies also have plans to install BESS at locations where they are allowed to construct, own, and operate solar generation facilities. G.L. c. 164, §1A(f).

Eversource

Overview of BESS demonstration projects

In 2017, the Department of Public Utilities (DPU) approved 2 battery energy storage systems (BESS) as part of Eversource's base distribution rate case (D.P.U. 17-05, pages 455-471).  These 2 projects were intended to:

• defer transmission and distribution investments,
• improve reliability, 
• reduce fossil fuel use, and 
• evaluate other potential use cases. 

The DPU initially approved the following 2 demonstration projects:

• Wellfleet/Outer Cape: 25 megawatt (MW) / 38 megawatt hours (MWh)
  • For any BESS project, MW refers to the rated power capacity and MWh to the energy capacity. Together, these numbers indicate how quickly a BESS can charge or discharge and for how long. For example, a 5 MW / 10 MWh BESS can discharge at 5 MW for about 2 hours.
• Martha’s Vineyard: 5 MW / 20 MWh

Eversource has reported on the progress of these projects as part of its grid modernization annual reports.

Wellfleet/Outer Cape project

The Wellfleet project evolved into the Outer Cape project, with a BESS located in Provincetown. This BESS was placed into service on December 1, 2022, with a 25 MW / 38 MWh storage capacity. Since then, the facility has provided backup power for local customers during adverse weather events and abnormal system conditions. For more information on this project:

• Outer Cape energy storage implementation report
• Outer Cape battery energy storage system

Martha’s Vineyard project

On May 17, 2021, Eversource notified the DPU that it cancelled the Martha’s Vineyard BESS project. After a new analysis, Eversource found the project was no longer a good financial investment. Two main factors changed:

• The price of the project went up, and
• The updated analysis showed different energy needs than forecasted.

For more information on this project, visit Eversource update regarding Martha’s Vineyard battery energy storage project.

Solar and BESS

As part of its 2025‑2029 Electric Sector Modernization Plan, Eversource proposed a 1 MW / 2 MWh mobile BESS in Springfield. For more information on Eversource’s mobile BESS projects, visit Eversource's mobile battery energy storage system.

In D.P.U. 22-64 and D.P.U. 22‑65, Eversource has proposed constructing, owning and operating solar generation facilities paired with BESS on company-owned land in:

• Yarmouth (2.1 MW solar / 0.6 MW BESS), 
• Brockton (1.89 MW solar / 0.3 MW BESS), and 
• Lawrence (1.02 MW solar / 0.25 MW BESS). 

These projects are pending before the Department. Visit Solar facilities owned by the electric and gas companies for more information. 

National Grid

National Grid has installed BESS at several locations where the company owns solar generation facilities:

• Shirley (2 locations at 1 MWh each),
• Charlton (1.98 MWh),
• Northbridge (1.5 MWh stationary BESS and 0.5 MWh mobile BESS),
• Attleboro (1 MWh), and
• Grafton (3.075 MW/8.071 MWh).

Unitil

In 2021, Unitil installed a 2 MW / 4 MWh BESS at its Townsend substation. Unitil designed the project to:

• Use the energy stored to reduce load during key hours of the day, and
• Avoid the need for future upgrades at the substation.

Visit Unitil battery energy storage system for more information on this project. 

Last updated:	July 1, 2026