North American Electric Reliability Corp reported deployable reserves shrinking due to rising forced outage rates in coal and gas generation (39.8 TWh and 19.1 TWh increases in 2025).

Coal and gas generation experienced significant capacity challenges in 2025, with coal units reporting 39.8 TWh and gas units 19.1 TWh of unavailable energy, according to the North American Electric Reliability Corporation.

The underlying issue stems partly from aging infrastructure. "Most large coal units are over 40 years old and are expected to be retired in the relatively near future," NERC noted. These facilities were not originally designed for the frequent on-off cycling now required in many grid regions. "These 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. These factors compound to increase the likelihood of failure over time."

Large industrial loads, particularly data centers, are introducing new reliability considerations. In February 2025 alone, two separate events demonstrated the scale of potential disruptions: a transmission fault in the Eastern Interconnection triggered 1.8 GW of customer-initiated load reduction, while another incident resulted in 428 MW of data center curtailment. "These events demonstrate that the reliability challenges from large loads will increase as these facilities become more prevalent on the grid," NERC stated. "It remains important for grid planners and operators to understand and study the expected performance of the large load facilities during grid disturbances."

The power system is undergoing rapid transformation as conventional generation retires and gets replaced "primarily by natural gas and increasing inverter-based resource penetration." Wind, solar, and battery storage are expanding quickly, introducing operational complexity. Regions with reduced inertia, high renewable penetration during light-load periods, or rapidly shifting power flows face particular challenges in maintaining stability.

Battery energy storage systems (BESS) have emerged as a critical technology, growing at rates matching solar expansion since 2022. However, the sector faces emerging risks. In January 2025, a 300-MW BESS facility experienced thermal runaway during routine testing that "ultimately resulted in the functional destruction" of the warehouse-style facility. "While outages internal to the plant regularly occur with other generation resources of similar or greater capacities, the permanent, unplanned loss of a non-BESS facility is exceedingly rare," NERC observed. "As such, this type of failure represents a risk consideration unique to BESS that needs to be taken into consideration as the resource continues to expand."

Despite these concerns, NERC does not view current BESS failures as threatening overall system reliability. Battery systems provide valuable services by smoothing load curves and enabling conventional generators to operate with longer ramp periods. This reduces wear on aging thermal plants not designed for daily cycling. However, BESS cannot substitute for long-term resilience during major events like winter storms, as their limited capacity restricts them to frequency support "until additional resources can come on-line for indefinite system support."