Not the Result of Any Particular Event: Rising Forced Outage Rates in NERC's 2026 State of Reliability Overview

NERC, the North American Electric Reliability Corporation, delivers its State of Reliability in two parts, an overview and a technical assessment. The overview for 2026 is dated June 24, 2026, and one of the trends it names is that conventional generation forced outage rates are up. Forced outage performance, it says, is "a foundational indicator of BPS reliability," because it shows whether generating resources can perform daily as well as when they are most needed, in periods of high demand, stressed system conditions and extreme weather. BPS is the bulk power system. Parts of the overview follow, not the whole.

Above Historical Norms

In 2025, the overview says, the annual weighted equivalent forced outage rate of conventional generators, or WEFOR, rose to 9.2%, "compared to historical norms rarely exceeding 8%." Coal and combined-cycle units were the primary drivers, with increases of over 39.8 TWh and 19.1 TWh of unavailable energy year over year. WEFOR, a footnote explains, looks at how much units' time and generating capacity is reduced "due to forced outages and derates relative to the amount of time they could be generating," weighted by each unit's net maximum capacity.

The data come from the Generating Availability Data System, or GADS. Reporting to it "is mandatory for units with a capacity >20 MW owned by NERC-registered Generator Owners (GO)," and the conventional data set is separate from wind, solar and hybrid energy storage.

"This increase was not the result of any particular event but an increase distributed across most months throughout the year, with three months’ WEFORs being comparable to the months when winter storms Elliott and Uri occurred." In the overview's words, "The lack of specific major events is indicative of a more subtle baseline increase in conventional forced outage rates." As WEFOR increases, it adds, planning reserve margins may also increase at a higher rate to accommodate the uncertainty.

By Fuel Type

"Further analysis (see Table 2) identified that the increase in unavailability was primarily driven by a variety of combustion-based generators. The largest year-over-year increases in TWh of unavailability were observed in coal (39.8 TWh increase from 2024 to 2025) and combined-cycle units (19.1 TWh increase from 2024 to 2025)." Weighing that with each type's installed capacity and WEFOR, the overview identifies coal-fueled generators "as being of more concern than others."

The table sets the two years side by side. Some of its rows, with what it gives under "2024 WEFOR" and under "2025 WEFOR":

• "Gas - Simple Cycle Combustion Turbine": 20.7% and 22.8%.
• "Combined Cycle": 4.2% and 5.7%.
• "Coal": 11.2% and 14.1%.
• "Total/Overall": 7.6% and 9.2%.

A fleet's rate is a weighted average across many units and owners, not a forecast for one machine. For a campus that leans on its own turbines with no grid behind them, it is a reason to ask how much spare capacity stands behind each unit.

What the Owners Said

NERC and the Regional Entities asked "the owners of 41 generators that had a year-over-year increase of at least 1 TWh" of unavailability to voluntarily provide more context, and responses came back for 26 of them. Of the cutoff, a footnote says, "The exact 1 TWh amount provided a clean cut point with a sufficient population but was ultimately arbitrary."

"Sixteen of the units experienced equipment destruction extensive enough to significantly prolong their 2025 outage(s)." "Eight of the units indicated that supply chain constraints significantly prolonged their 2025 outage(s)," with the constraints "all indicated as occurring at the manufacturer," though they "may have occurred deeper into the supply chain unknown to the Generator Owner (GO)." Among them were being unable to obtain materials for the repairs, trouble locating part specifications, inexperienced project management and a lack of staff. "Six of the units indicated complete or partial turbine blade release or vibration, which, upon further inspection, would have likely resulted in eventual release." Multiple units also used the downtime for additional maintenance and inspections, which some said extended their outages but brought future benefits.

Among the cause code component groups NERC trended since 2016, high, intermediate and low pressure turbine components "represent the largest, most consistently increasing group if combined." It adds that further analysis of these groups and their cause codes "are necessary," and that the results "align with, but do not prove, industry assertions concerning coal and combined-cycle units." Most large coal units "are over 40 years old," and large coal and combined-cycle units "were not designed for regular cycling, which has become an operational requirement in some areas and a necessity to maintain economic viability in others."

What NERC Recommends

"NERC and the relevant stakeholders should consider adjusting or at least be prepared to adjust reserve requirements to account for lower conventional generation availability." Generator owners should consider bolstering turbine inspection procedures, and "should ensure that manufacturers have capability and plan to replace major components in the event of failure."

For manufacturers, the overview says they "should consider immediately increasing the number of trained technical maintenance personnel," citing the increasing frequency of outages with major equipment failure and a lack of adequate or experienced staff. And "Manufacturers should verify material procurement and processing capabilities."