Interregional transmission is critical to the electric power system of the US, allowing regions to transport energy between one another in periods of need. An expanded network of interconnected transmission not only improves reliability by providing access to additional power generation sources in the face of uncertainties such as fuel or generation loss, transmission outages, and extreme weather events, but also enhances system stability by expanding the geographic diversity of variable energy resources.
The urgent need for more interregional transmission has only increased in recent years, due to the increasingly frequent and severe weather events. The lack of interregional transfer capacity between nearly every neighbouring grid region is putting the American grid at risk.
A host of studies have been carried out in the past, determining the transmission needs of the US, viz. the National Transmission Needs Study (2023); National Transmission Planning Study (2024); Atlantic Offshore Wind Transmission Study (2024); GE and Natural Resources Defense Council (NRDC): Benefits of Interregional Transmission Capacity (2022); Massachusetts Decarbonisation Pathways Roadmap (2020); Lawrence Berkeley National Laboratory (LBNL): Empirical Estimates of Transmission Value (2022); National Renewable Energy Laboratory (NREL) Interregional Renewable Energy Zones Study (2024); Massachusetts Institute of Technology – Center for Energy and Environmental Policy Research (MIT-CEEPR) QC Hydro and Northeast Decarbonisation (2020); and the North American Electric Reliability Corporation (NERC) Interregional Transfer Capability Study (ITCS) (2024).
These transmission studies have shown the importance of interregional transmission. However, they do not translate into actionable projects for several reasons, mainly because the existing interregional coordination processes fall short of addressing the identified interregional needs and realising the associated benefits. Thus, while numerous studies have documented the benefits of interregional transmission and regional planning processes that successfully enable transmission development, there are several gaps and barriers that have prevented the development of beneficial interregional transmission projects. No process currently exists for groups of states spanning different transmission planning regions to take the various steps necessary to identify, evaluate, select, and agree to share the cost of beneficial interregional transmission projects so they can be developed.
Working in this direction, the Northeast States Collaborative on Interregional Transmission (Collaborative) comprising nine states – Connecticut, Delaware, Maine, Maryland, Massachusetts, New Jersey, New York, Rhode Island and Vermont – released the Strategic Action Plan on Interregional Transmission (Action Plan) on April 28, 2025, for state and federal policymakers, and independent system operators/regional transmission organisations (ISOs/RTOs), to pursue interregional transmission solutions to reduce costs for consumers and make grid systems secure. The Collaborative also hosted a webinar on April 29, 2025 to discuss the Action Plan’s near-and mid-term focus areas. The Action Plan identifies gaps in today’s interregional transmission planning processes and recommends actions that states can take to improve grid reliability, support economic growth, and reduce costs for consumers across the Northeast.
Highlights of the Action Plan…
Background
In 2023, New York participated in a request to the US Department of Energy (DOE) to convene a multi-state group called the Northeast States Collaborative on Interregional Transmission, to explore mutually beneficial opportunities to increase the flow of electricity between the ISO New England (ISO-NE), New York ISO (NYISO), and PJM Interconnection planning regions. Following this, in the summer of 2024, the multi-state group signed a memorandum of understanding (MoU) to establish a framework for coordinating its activities and identified the Action Plan as the next step. The states were represented by their public department services or energy administrations – the Connecticut Department of Energy and Environment Protection; Delaware Division of Climate, Coastal and Energy; Maine Governor’s Energy Office; Maryland Energy Administration; Massachusetts Executive Office of Energy and Environmental Affairs; New Jersey Board of Public Utilities; New York State Energy Research and Development Authority (NYSERDA) and New York State Department of Public Service (DPS); Rhode Island Office of Energy Resources; and Vermont Department of Public Service. The Collaborative has engaged relevant federal agencies and organisations with technical expertise to identify and assess shared areas of focus for interregional transmission cooperation, and remove regulatory and technical barriers towards this objective.
Current gaps
The Action Plan aims to identify beneficial interregional transmission expansion opportunities and make them actionable through existing regional planning processes. It identifies the so called “missing middle” in grid planning: the absence of a process for states to collaborate on interregional transmission projects.
The plan is intended to help advance the Collaborative’s work by focusing its efforts over the near term (2026) and mid term (the next several years).
The interregional transmission between New York, New England and PJM is highly valuable in the near term and long term, and low-regret expansion opportunities should be pursued. By 2035, it is estimated that adding 2 GW of additional transfer capability between New York and PJM would be a low-regret expansion (before considering the value of transmission for decarbonisation), with a similar 1.7 GW incremental low-regret need between New York and New England prior to considering decarbonisation-related benefits. By 2040, these low-regret needs are expected to grow to 4 GW between PJM and New York and to 3 GW between New York and New England (before accounting for decarbonisation targets). Assuming that decarbonisation targets are met, beneficial transmission additions by 2040 are expected to be much larger: 4.5-6 GW between New York and PJM, and 4-7 GW between New York and New England. The studies also highlighted the long-term need for expansion between the Northeast and Canada (By 2050, 10 GW between Canada and Northeast is low-regrets).
Near-term action plan
The near-term action plan outlines short-term steps necessary to identify, evaluate, select, and provide opportunities for states to agree on sharing the cost of beneficial interregional transmission projects, enabling their development. Over the next year, the plan identifies priority actions for the Collaborative to pursue to promote the development of interregional transmission projects, with the ultimate objective of providing reliability benefits and cost savings to the regions’ electricity consumers. For addressing the current gaps in interregional transmission initiatives, it recommends two discrete actions – identify beneficial projects and propose them to ISOs/RTOs; and develop cost allocation for these projects.
RFI for project designs
According to the plan, the present process creates a “triple hurdle”, requiring the potential projects to be approved separately by each planning region and again in a joint evaluation exercise. Hence, for the project identification process, the plan calls for the development and issuance of a request for information (RFI) for project designs that could meet the low-regrets interregional transmission needs identified in previous studies (mentioned above). The RFI would encourage the submission of project ideas on either the PJM–NYISO or NYISO–ISO-NE interregional seams, allowing for both offshore and onshore transmission solutions as well as solutions that are synergistic with the regions’ need to create the grid capacity necessary to integrate clean-energy resources, such as offshore wind (OSW) generation. Once RFI submissions are received, the Collaborative would be able to conduct an initial assessment of each project, and together with the RTOs/ISOs invite those projects demonstrating the most beneficial expansion opportunities to present their concepts in detail. Following consideration of any feedback received and taking into account ongoing activities within the RTOs/ISOs, the Collaborative could then consider a formal request to the Joint ISO/RTO Planning Council (JIPC) to evaluate one or more of the identified projects from a multi-value perspective that meets the Collaborative’s objectives.
Cost allocation of projects
The plan suggests that states across these three Northeastern market regions will need to agree on a framework for identifying benefits and sharing the costs of any interregional investments. To supplement that framework, the Collaborative could consider issuing an open invitation for comments and/or alternative cost allocation structures for interregional transmission investments. Based on this discussion and subsequent evaluation, the collaborative may finalise guidelines or develop model tariff rules for interregional transmission cost allocation.
Uniform HVDC design standards
Currently, the ISO-NE and NYISO (as part of the Northeast Power Coordination Council – NPCC) do not permit the 525 kV bi-pole high voltage direct current (HVDC) technology to deliver 2 GW from OSW facilities based on caps on each region’s most severe single contingency (MSSC) level assuming the entire bi-pole transmission system would be lost. The Collaborative has already engaged with the three planning regions and the JIPC to evaluate the circumstances under which the MSSC level could be raised. Parallelly, the DOE has created a recent funding opportunity to assist the Collaborative in developing technical standards associated with future development of the latest interoperable HVDC equipment that would be enabled by revisions to how the MSSC is defined. This effort – known as the Planning Offshore Interregional Network Standardization (POINTS) Consortium – will fund a consortium managed in collaboration with ConnectWerx to develop recommendations for technology standardisation for OSW HVDC projects to ensure that future HVDC facilities are capable of being networked with each other, enabling the potential for future beneficial connections between offshore collector platforms in multiple states and regions.
Optimisation of state OSW and transmission procurements
To procure OSW generation resources, each state carries slightly different statutory and regulatory requirements that result in customised procurement frameworks. In the near term, the Collaborative should consider working in close coordination with relevant agencies within each state, identifying best practice contract language for OSW generation. The areas of potential alignment in state procurements could include incorporating a network-ready standard for export cables; creating the option to convert export cables into open access transmission facilities in the future (should they become networked); developing bid evaluation criteria to reflect the value of proposals that offer regional/interregional transmission solutions (including attributing value associated with landing points and lease areas that could facilitate linking of individual export cables); combining state procurements into multi-state efforts to achieve the scale needed for cost-effective transmission solutions; and preserving contracting flexibility and coordinating the timing of OSW targets to accommodate in-service dates that would avoid supply-chain bottlenecks (and achieve more cost-effective outcomes).
Develop interregional coordination principles for Order 1920 compliance filings
At present, there is limited focus being paid by RTO/ISO to the updated requirements of the Federal Energy Regulatory Commission’s Order 1920 regarding interregional coordination. Hence, there is a need to develop a set of interregional planning principles outlining how ISOs assess and calculate interregional project benefits. These benefits should not be limited to the least-common denominator subset of different benefits estimated by each region but should include all benefits considered by neighbouring regions. Further, it should address the state’s desire to remove timing challenges and other process limitations associated with the current interregional planning. These principles can be incorporated within the Order 1920 interregional coordination compliance filings, which are due by August 2025.
Support reducing seams-related inefficiencies
It is well documented that existing interregional transmission facilities are poorly utilised and that RTOs/ISOs often do not recognise in their planning efforts the value that interregional transmission provides in terms of energy trading, resource adequacy, or grid resilience. Hence, it is essential to resolve seam-related inefficiencies, including by advocating for intertie optimisation, and to encourage regions to assess and consider the benefits of better utilised interregional facilities within improved planning processes.
Mid-term action plan
Tariff revisions
In preparation for moving forward with candidate interregional projects once they have been identified through a near-term project identification process (example projects proposed in response to an RFI process discussed above), the Collaborative should work with the RTOs/ISOs to develop the necessary revisions to their market rules to enable the evaluation and selection of identified beneficial interregional projects. These revisions would also implement the collaborative’s preferred cost allocation for the specific interregional project. Projects that satisfy the selection criteria could then be eligible for cost allocation under the framework identified by the Collaborative through the near-term actions.
Multi-state buying pool for standardised HVDC and other transmission equipment
As an additional step towards standardising equipment utilised in future interregional transmission and OSW procurements, the Collaborative is exploring the creation of a multi-state buying pool for standardised HVDC and other transmission equipment. The buying pool would serve as a centralised mechanism for coordinated bulk orders of HVDC equipment (including potentially HVDC submarine cable) that, once deliverable by the manufacturers, can then be utilised by state-selected OSW facilities.
Enable the transition from generator export lines to network transmission facilities
As part of future networked transmission systems, facilities currently operated by generation developers as generator export lines would also be networked with onshore transmission facilities. This would impose a new set of responsibilities on the OSW developer, that of a transmission owner, subject to open access standards. To enable this transition, the Collaborative should identify the necessary contractual and regulatory frameworks that could be adapted by the Northeastern RTOs to create networked offshore grids. This will likely require mechanisms to preserve existing rights while making unused transmission capability available for system use — like the California ISO’s recently FERC-approved “subscriber participating transmission owner (PTO)” model, which compensates the owner of the transmission facility (in this case, the OSW generator who funded the tie-line through state contracts) for any use of the facility beyond subscriber contracts while enabling beneficial transfers on the available capacity to reduce customer costs. The RTOs should also be engaged to ensure the ultimate feasibility and efficient operations of such offshore transmission frameworks.
A range of values are reported across different studies for existing interregional transfer capability, which partially explains the differences in additional transfer capability needs across these studies.
Source: Northeast States Collaborative’s Action Plan
The way forward
Through the latest strategic plan initiative, the nine Northeast states have come out with an arrangement to mitigate the inter-regional planning gridlock and have taken long-term grid operations in their own hands. The release of the action plan clearly indicates a shift in the governance by placing the states in the lead, and the Collaborative provides a unique opportunity to address the inter-regional transmission challenges.
