Brattle Experts Issue Whitepaper Reviewing ISO-NE’s Evaluation Framework for Transmission Proposals
The Independent System Operator of New England (ISO-NE) is currently implementing its first long-term transmission planning (LTTP) solicitation at the request of the New England States Committee on Electricity (NESCOE). In a new whitepaper sponsored by National Grid Ventures, Massachusetts Municipal Wholesale Electric Company, and Energy New England Transmission, Brattle experts evaluate the LTTP process – a major step forward in more effective, proactive transmission planning that identifies long-term strategic investments that deliver value to New England consumers – and recommend enhancements to ensure the selected transmission project delivers maximum value.
Solicitations from Transmission Developers
ISO-NE’s first LTTP solicitation sought transmission proposals that increase transfer capability from Maine to southern New England, enabling the identification of strategic long-term investments that reduce long-term system costs, address persistent transmission constraints, and allow for the delivery of low-cost renewable resources.
To maximize customer benefits, NESCOE encouraged developers to propose cost-effective, expanded-scope solutions that increase transfer capability of the required interfaces beyond minimum thresholds and upgrade additional interfaces. The solicitation thus represents an opportunity to make upgrades to critical transmission interfaces that will benefit customers for decades.
Transmission developers submitted LTTP proposals that roughly fall into two categories:
- Onshore high-voltage alternating current upgrades between Maine and New Hampshire that meet at least the minimum requirements of the LTTP solicitation; and
- Subsea high-voltage direct current (HVDC) links between Maine and the Boston area that provide an expanded scope of upgrades beyond the LTTP’s minimum requirements.
ISO-NE’s initial screening analyses identified concerns with the specific designs of four out of the six proposals received, including all the expanded-scope HVDC links, that lead to an initial disqualification notice. Proposal submissions and ISO-NE’s analyses are under review, which may allow currently disqualified proposals to continue to the next phase of the LTTP evaluation.
To select a winning solution from the qualifying LTTP proposals, ISO-NE will rely on several quantitative benefit metrics and a broad set of additional evaluation factors.
Recommendations
The white paper, “Considerations for Selecting the Most Beneficial Proposal in ISO-NE’s 2025 LTTP Request for Proposal,” evaluates ISO-NE’s benefit metrics and evaluation factors and recommends enhancements to ensure the LTTP proposals are accurately evaluated so that the selected solution will provide customers with the largest net benefits. The evaluation identifies elements of the current ISO-NE framework that do not fully capture the value of LTTP proposals and, as a result, are likely to introduce a bias against expanded-scope solutions – particularly where quantitative metrics understate consumer benefits from avoided local resource costs, production costs and congestion savings, and avoided transmission investment.
The authors explain that ISO-NE can improve the LTTP evaluation within its current framework through sensitivity analyses that capture missing value and allow for appropriate weighing of additional evaluation factors. The recommended improvements will help ISO-NE select the most cost-effective, highest-value project for New England consumers, consistent with NESCOE’s objectives.
The full white paper, authored by Principals Johannes Pfeifenberger and Michael Hagerty, Senior Energy Associate Linquan Bai, and Energy Associate Peter Heller, is available below.
To explore these issues in more detail, please join Brattle for a webinar on Tuesday, June 2 at 12 p.m. (ET), where we will discuss the evolving LTTP process in New England and examine how ISO-NE’s first solicitation represents a significant step toward more proactive, value-driven regional transmission planning. Please find more information below.
