Planning
The backbone of the region’s power grid is its high-voltage transmission system — 9,000 miles of wires, as well as substations and other equipment that bring electricity from the places where it’s generated and stored to places where it’s distributed to homes and businesses. Planning the future of this system is one of our three critical roles, and several ongoing projects support this need.
Today, the transmission system in New England is strong. Over the past two decades, the region has made significant investments in this system to protect reliability and serve the electricity needs of New Englanders. These investments have also allowed for the retirement of many older power plants and created market efficiencies by reducing congestion and out-of-market energy costs. But in the next two decades and beyond, the transmission system must become significantly more robust if it is to continue meeting the region’s changing needs.
Resources like wind and solar generators and battery storage facilities are usually smaller than traditional fuel-fired power plants and more dispersed across the region. As renewables, storage, and electrification increase, more electricity will flow farther, from rural areas with more resources to urban areas with higher demand. Several key system planning projects underway at ISO New England are designed to support upgrades needed to meet these changing needs, while providing oversight to keep costs reasonable.
Longer-Term Transmission Planning and Order 1920
Developers are proposing elective transmission upgrades that would deliver clean energy from remote areas to the places in New England where demand is greatest. Also, assuming state electrification and environmental goals are met, the ISO projects that, by 2050, more than half of the regional transmission system could face thermal overloads during times of peak demand.
The ISO’s longer-term transmission planning (LTTP) process is designed to address these policy-driven needs. At the direction of the New England States Committee on Electricity (NESCOE), in spring 2025 the ISO issued a request for proposals to develop solutions that would enhance the market efficiency and reliability of the regional transmission system. The request for proposals was based on results from the ISO’s landmark 2050 Transmission Study, which identified several “roadmaps” for mitigating potential longer-term risks and estimated costs associated with each approach.
NESCOE’s request is aimed at upgrading the transmission system between northern Maine, where land-based wind generation is expected to increase, and the more populous regions of southern New England, where demand for electricity is highest. The ISO completed its evaluation of proposals in summer 2026. NESCOE now has several months to decide whether to move ahead with the ISO’s selection of the preliminary preferred project.
Many elements of this landmark effort align with FERC Order No. 1920, which also addresses longer-term transmission concerns. The ISO is working with the states and other stakeholders to decide how Order 1920 and LTTP will be combined or work in parallel to ensure the region’s transmission system maintains its current high standard of reliability.
Our Role as Asset Condition Reviewer
As the grid evolves, it does so in the context of an aging transmission system. Some components of New England’s grid are decades old. Transmission owners are proposing a growing number of upgrades — known as asset condition projects — designed to refurbish deteriorating facilities.
Historically, the ISO has had limited involvement in asset condition projects, which are the purview of transmission owners and FERC. But following discussions with stakeholders in 2025, we agreed to an advisory role as asset condition reviewer to provide added oversight and independent evaluation. The ISO is the first system operator in the nation to take on such a role, the details of which were filed with FERC in summer 2026. The proposed review process will involve assessing the need for each project, evaluating alternatives, and reporting findings to stakeholders.
Interconnection Reforms to Improve Efficiency
Before a new resource can connect to the grid, we conduct a series of technical analyses — called interconnection studies — to ensure it can receive transmission service reliably. In 2015, power plants fueled by natural gas represented over half the requests in the queue for ISO New England interconnection studies. Between 2015 and 2025, requests in the queue grew by 80%, with wind, solar, and storage (primarily short-duration batteries) accounting for more than 99% of proposed resources.
The growth of proposed resources and change in queue composition required a new strategy. FERC Order Nos. 2023 and 2023-A and ISO New England’s resulting interconnection process changes ease backlogs by prioritizing projects with a high likelihood of development and deterring speculative ventures. The revised process has a “first-ready, first-served” focus. It requires new generating facilities to complete studies as a group, or cluster, rather than one after another, streamlining the study process. The first cluster study will open in October 2026, and a transitional cluster study was completed in summer 2026.
Cooperation is Crucial
Successfully meeting the transmission challenges ahead will take coordination between the New England states, developers, and the ISO. Future projects may face obstacles in the form of siting and permitting restrictions, local opposition and lawsuits, supply chain delays, and financing difficulties. It will be crucial for the states and industry to decide how to share the costs of these infrastructure investments, as well as how to work through siting and permitting delays. The ISO stands ready to provide technical analysis to help the states as transmission planning needs evolve in the years ahead.