The state’s Independent System Operator is forecasting power grid reliability concerns in New York City and Long Island as early as next summer – with broader concerns raised in a second ISO report issued earlier this week.

The NYISO’s third-quarter Short-Term Assessment of Reliability (STAR) studies electric system reliability over a five-year period from July 15, 2025, through July 15, 2030, and identifies reliability violations in New York City and Long Island beginning in the summer of 2026. The violations are driven by generator deactivations, increasing consumer demand, and transmission limitations. The STAR report is final.

The ISO also released its 2025-2034 Comprehensive Reliability Plan. The plan is issued every two years and sets the ISO’s plan to maintain a reliable electric grid over a 10-year planning period. The Comprehensive Reliability Plan warns that the New York state electric system faces an era of reliability challenges driven by the aging of the existing generation fleet, the rapid growth of large loads from data centers and semiconductor manufacturing and the difficulty of developing new supply resources due to public policies, supply chain constraints and rising costs for equipment. The CRP was issued this week in draft form and is expected to be final in November.

“Taken together, these two reports show the grid is at a significant inflection point,” said Zach Smith, Senior Vice President of System and Resource Planning for the New York Independent System Operator. “Depending on future demand growth and generator retirements, the system may need several thousand megawatts of new dispatchable generation within the next 10 years.”

The reliability needs identified by the STAR in New York City and Long Island are based on a deficiency in transmission security. Transmission security analysis tests the ability of the power system to withstand disturbances, such as electric short circuits or unanticipated loss of a generator or a transmission line, while continuing to supply and deliver electricity to consumers during peak demand when the system is stressed. Finding a reliability need begins a process administered by the ISO to bring reliability margins back to acceptable operating levels. The ISO will begin the process immediately by working with the local utilities and the marketplace to identify and evaluate possible solutions. Transmission, generation, energy efficiency or a combination of each can qualify as solutions through the process.

Considering the unprecedented changes happening across the bulk electric system, the CRP uses several informational scenarios to examine the impacts of key risk factors and capture possible outcomes for grid planning purposes. Major factors that influence the scenarios include aging generation, variable demand forecasts, weather variability, and ongoing delays in developing additional resources. The CRP also shows different scenarios of resource additions to demonstrate potential solutions to support long-term grid reliability.

Environmental advocates, on the other hand, said earlier this year that the ISO’s assumptions are misleading and asked Gov. Kathy Hochul, Public Service Commission Chair Rory Christian, Department of Environmental Commission Commissioner Amanda Lefton, and New York State Research and Development Authority President Doreen Harris to scrutinize NYISO’s actions and narratives, and to push for and prioritize systemic reforms that will accelerate the transition to affordable, reliable, renewable energy.

Since 2021 ISO reliability reports have noted that reliability margins are declining – including projected shortfalls starting this year in New York City with the pending retirement of several peaker plants that were to be taken offline. Those plants remain online until the Champlain Hudson Power Express transmission line from Quebec, Canada, to New York City is completed in 2026.

Current statewide reliability margins in winter are sufficient, according to an ISO ISO Power Trends report released earlier this year, but if gas-fired generators cannot secure fuel during peak winter demand periods, statewide deficiencies could arise as soon as winter 2029-2030 under normal weather conditions.

The group of environmental advocates say none of the earlier ISO reports on which the most recent Power Trends report bases its analysis concluded that fossil fuel generation is necessary for grid reliability or that repowering aging gas plants is beneficial. The advocates say the ISO reports have also said there is growing unreliability of gas-fired power, noting aging plants are breaking down more often, have high costs and are not reliable for winter peak demands.

“By publishing this misleading summary Power Trends report, NYISO is standing in the way of the clean energy transition New Yorkers need and the law requires,” said Rachel Spector, Deputy Managing Attorney for the Northeast Regional Office at Earthjustice. “NYISO’s failure to prepare the grid for a clean energy future is putting our climate goals, our wallets, and our health at risk. We urge state leaders to take a hard look at NYISO’s track record and misleading messaging – and to act swiftly to remove the barriers standing in the way of New York’s clean energy progress.”