Duke Energy Carolinas Emergency Order Targets Heat-Driven Grid Risk
The Department of Energy issued a Section 202(c) emergency order allowing Duke Energy Carolinas to use specified generation and backup resources as extreme heat pushes forecast electricity demand above 22 GW.
Published · Updated · 4 min read
The U.S. Department of Energy issued a Duke Energy Carolinas emergency order on September 3 authorizing additional generation and backup resources to support grid reliability in North Carolina and South Carolina as extreme heat drives unusually high electricity demand across the utility’s service territory.
Duke Energy told federal officials that peak demand was forecast at approximately 22,295 MW on September 3 and 21,773 MW on September 4. The utility said it had secured an additional 2,677 MW of capacity and expected demand-management measures to reduce electricity demand by more than 400 MW, but warned that firm load curtailments could still become necessary under stressed conditions.
The Department of Energy’s Section 202(c) order authorizes Duke Energy Carolinas to dispatch specified generating units and order their operation when needed to maintain reliability.
The order also allows Duke, working with transmission owners and electric distribution companies, to direct backup generation resources to operate as a last resort before an Energy Emergency Alert 3 or during an EEA 3.
That provision highlights the potential grid value of distributed generation that normally sits behind customer meters. Backup generators, batteries and other controllable resources can reduce the amount of electricity a large customer draws from the grid during an emergency, although their capabilities, emissions and operating constraints vary significantly by technology.
The same principle is increasingly relevant as utilities plan for more distributed and flexible resources. Microgrid Media’s coverage of large-load grid planning in Houston examined how demand response, on-site generation, batteries and microgrids can affect the amount of firm grid capacity required to serve major electricity users.
Duke forecast more than 22 GW of peak demand
The underlying Duke Energy Carolinas emergency application provides more detail about the conditions that led to the federal action.
Duke said a strong upper-level ridge was producing an extended period of extreme heat, with system-average temperatures expected to reach approximately 96°F on September 3 and 97°F on September 4. Heat-index values were expected to reach 100°F to 105°F in parts of the service territory.
The utility said the consecutive hot days were increasing residential and commercial cooling demand while warm overnight temperatures limited the recovery of air-conditioning equipment.
Duke also said it had initiated emergency operating plans. Measures included curtailing recallable energy sales, implementing load-management programs, using residential demand response and large-load curtailments, securing external capacity where available and committing available generation resources.
Some generation faces environmental operating constraints
The federal order does not mean the Carolinas had already entered widespread load shedding. Instead, it gives Duke additional tools if normal operating measures prove insufficient.
Duke’s filing said some generating units can face output limitations associated with environmental permits, including emissions and other operating restrictions. The company requested temporary federal authorization to operate specified resources beyond those constraints when necessary for grid reliability.
The filing also covers customer-owned backup generation that may be able to disconnect from the grid and carry local loads during the emergency. Duke said such generators can themselves face emissions or runtime restrictions, which is why they were included in the request.
The American Public Power Association independently reported that DOE issued the order to mitigate blackout risk during the hot-weather event and confirmed that backup generation can be directed as a last-resort reliability measure.
The event illustrates the difference between reliability and resilience
Short-duration grid emergencies expose the relationship between conventional generation, transmission infrastructure, demand response and distributed backup resources.
Microgrid Media recently reported that distribution-grid upgrades in New Jersey produced measurable reliability improvements on selected circuits, illustrating a different approach to reducing outage risk through longer-term infrastructure investment.
Microgrids can provide another layer of resilience when they are designed to disconnect from the utility system and maintain critical loads locally. A microgrid controller, for example, can coordinate batteries, generators, renewable resources and loads during the transition from grid-connected to islanded operation.
The Carolinas event is a broader bulk-system reliability challenge rather than a microgrid deployment, but DOE’s authorization of customer-owned backup generation demonstrates how behind-the-meter resources can become part of emergency grid operations when system conditions tighten.
DOE’s order took effect September 3 and is scheduled to remain in force through September 8. The department’s order extends beyond the shorter period Duke initially requested in its application.
Whether any specific generating units or customer backup resources ultimately operate under the emergency authorization will depend on actual grid conditions and Duke’s dispatch decisions. The existence of the order therefore should not be interpreted as evidence that blackouts or emergency generation occurred.
The more important near-term indicator will be whether electricity demand and available generation remain balanced as the heat event continues through September 4 and temperatures begin to moderate.
