Massachusetts Awards 1.3 GW in First Major Energy Storage Procurement

Legislative Foundation

Massachusetts's first major utility-scale energy storage solicitation traces its origins to a sweeping piece of climate legislation signed by Governor Maura Healey in November 2024. Chapter 239 of the Acts of 2024 - formally titled An Act Promoting a Clean Energy Grid, Advancing Equity and Protecting Ratepayers - mandated that the state's electric distribution companies procure a total of 5,000 MW of operational energy storage capacity by July 31, 2030. The law expanded significantly upon Massachusetts' earlier 2018 goal of deploying just 1,000 MWh of storage by December 2025, a target the state was only partially on track to meet. By early 2025, utilities had 644 MWh installed with another 12,932 MWh in the pipeline.

The 5 GW mandate is structured by storage duration category: 3,500 MW is designated for mid-duration storage (four to ten hours), 750 MW for long-duration storage (ten to twenty-four hours), and 750 MW for multi-day storage (more than twenty-four hours), subject to commercial feasibility. The total energy capacity implied by the mandate is at least 39,500 MWh - a figure that reflects the state's view of storage not just as a peaking resource, but as a structural component of a net-zero grid.

The procurement authority flows through Section 83E of Chapter 169 of the Acts of 2008, as amended through successive legislation including Chapter 239. DOER was granted authority to develop a staggered procurement schedule in coordination with the state's three investor-owned electric distribution companies (EDCs): Eversource, National Grid, and Unitil.

What the Energy Storage RFP Was Seeking to Accomplish

The Section 83E Round 1 RFP was the first and largest single tranche of the statewide mandate, targeting 1,500 MW of mid-duration energy storage - specifically projects capable of discharging at full rated capacity for four to ten continuous hours.

Rather than procuring energy or capacity directly, the RFP sought environmental attributes only - specifically Clean Peak Energy Certificates (CPECs) under Massachusetts' Clean Peak Energy Standard (CPS). This structure means the long-term contracts provide a stable, bankable CPEC revenue floor while allowing developers to retain the full upside from participating in ISO-New England's wholesale energy, capacity, and ancillary services markets. It is a deliberate design choice that preserves market discipline while de-risking project financing.

The procurement targeted transmission-connected resources only (interconnecting at above 69 kV), with project sizes ranging from 40 MW to 1,000 MW nameplate capacity. All selected projects must achieve commercial operation by January 1, 2030. Contract terms were encouraged at up to 20 years, with a hard ceiling of December 31, 2050 and an explicit price cap - bids could not exceed 97.75% of the applicable Alternative Compliance Payment (ACP) rate, a meaningful constraint designed to protect ratepayers.

The EDCs' share of total procurement was allocated in proportion to their customer bases: Eversource at 53.89%, National Grid at 45.1%, and Unitil at 0.97%.

The Round 1 solicitation was explicitly designed as the first in at least four planned procurement rounds. Subsequent rounds, including Round 2 targeting approximately 1 GW, are expected to broaden the scope to include distribution-connected resources, longer-duration storage categories, and energy services in addition to environmental attributes.

The Bid Submission Process

The RFP timeline was aggressive and deliberately so. DOER and the EDCs filed a draft RFP with the Department of Public Utilities (DPU) on May 5, 2025, opening a public comment period. An Independent Evaluator reviewed the draft and concluded it was likely to attract competition and yield cost-effective results for ratepayers, while recommending improvements for future rounds including greater stakeholder input time and exploration of regional collaboration with neighboring states.

The DPU issued its final approval and the official RFP launched on July 31, 2025. A Bidders' Conference was held on August 14, 2025, drawing significant developer interest. DOER issued responses to bidder questions on September 2, 2025.

Proposals were due at 12:00 p.m. ET on September 10, 2025 - giving bidders less than six weeks from final RFP issuance to submission. This compressed window was widely understood to heavily favor well-capitalized developers with projects already advanced in the ISO-NE interconnection queue, as interconnection study processes typically span multiple years and represent the primary development risk in the region. Transmission interconnection costs in ISO-NE average approximately $230/kW and are a leading driver of project withdrawal from the queue.

Bidders were required to pay a non-refundable fee of $500/MW upon submission, demonstrate site control, and commit to ISO-NE's Capacity Capability Interconnection Standard. Bids with indexed or contingent pricing were explicitly excluded - a notable restriction given tariff and investment tax credit uncertainty during the submission window. Upon contract execution, developers face security deposit obligations of $40,000/MW, up to $60 million in aggregate.

Public versions of all submitted bids were posted to the Massachusetts Clean Energy website on the proposal due date.

The Bidders

Thirteen projects were submitted by the September 10 deadline, totaling approximately 1,500 MW in aggregate — essentially the full procurement target subscribed in a single round. All thirteen projects were transmission-connected. One - Bear Swamp - was a pumped hydro resource; the remaining twelve were BESS projects.

The partial list of submitted bids:

FlatIron Energy (four bids): Energizar · Hammersmith · Revolution · Salt Cod

CleanCapital (three bids): Brough Storage · Merlin Storage · Partridge Storage

Bear Swamp Pumped Hydro (Brookfield Asset Management)

Longroad Energy: Agawam Energy Center

Hecate Energy: Ward Hill Energy Center

East Point Energy: Hillman Energy Center

Rhynland Energy: River Mill Storage

Jupiter Power: Trimount ESS

The breadth of the bidder pool - spanning large-platform developers, independent power producers, and an incumbent asset owner - validated the state's thesis that the procurement structure would attract serious competition.

The 4 Energy Storage Projects Awarded

DOER announced Round 1 selections on December 19, 2025, approximately ten days later than the originally targeted December 9 announcement date. Four projects were selected, totaling 1,268 MW. The result fell short of the 1,500 MW maximum target, though state officials described the pool as high quality. The roughly 232 MW gap is expected to carry forward into the Round 2 solicitation scheduled for 2026.

The selected projects are:

Trimount ESS — Jupiter Power (Everett, MA) The standout project of the round. Trimount ESS will be built on the site of a former Exxon oil terminal - a 100-year-old fossil fuel facility in Everett - and is planned at 700 MW of capacity, making it by far the largest selected project. Beyond its scale, the project is projected to defer approximately $2.2 billion in regional transmission infrastructure upgrades, giving it strong ratepayer value credentials that likely weighed heavily in the evaluation.

Energizar — FlatIron Energy (Somerset, MA) Planned at 250 MW / 1,000 MWh, Energizar is expected to commence commercial operations in Q2 2027, making it potentially the first Round 1 winner to reach the grid. Its location in Somerset, on the southeastern coast of Massachusetts, positions it on existing industrial land near transmission infrastructure.

Salt Cod — FlatIron Energy (Chelsea, MA) FlatIron's second successful bid, Salt Cod is sized at 168 MW and is proposed for the site of the former Montaup coal-fired power plant - a brownfield redevelopment story that mirrors the Trimount ESS narrative and aligns with the state's environmental justice priorities.

River Mill Storage — Rhynland Energy (Tyngsborough, MA) Sited in Tyngsborough in the Merrimack Valley region, River Mill rounds out the four selected projects. The project's capacity has not been publicly disclosed in available sources.

Contract awards remain conditional. Final acceptance is subject to the successful negotiation of mutually acceptable long-term contracts between each winning developer and the three EDCs, followed by required regulatory approvals from the DPU. The EDCs were expected to file executed contracts with the DPU by April 24, 2026.

What Didn't Win - and What It Signals

Nine of the thirteen submitted projects were not selected: CleanCapital's three bids (Brough, Merlin, and Partridge), Longroad Energy's Agawam Energy Center, Hecate Energy's Ward Hill, East Point Energy's Hillman, Bear Swamp pumped hydro, and FlatIron's own Hammersmith and Revolution projects.

The concentration of awards - two projects to FlatIron, plus Jupiter Power and Rhynland - and the prominence of brownfield redevelopment sites among the winners suggest that site quality, transmission infrastructure proximity, and grid benefit metrics carried significant weight in the evaluation alongside price. Bear Swamp's exclusion is notable: despite being an operating asset with existing CPS qualification, the incumbent pumped hydro facility did not clear. Whether that reflects a pricing disadvantage relative to BESS at current equipment costs, or evaluation criteria that favored new capacity additions, has not been publicly disclosed.

DOER confirmed that Round 2 will expand eligibility to include distribution-connected resources - a structural change that will meaningfully broaden the competitive landscape and open future solicitations to a wider range of project types and developers.