Northern Virginia air and noise on backup generation

RICHMOND, Va. - A clause in a federal emergency order issued in September allowed the operator of the grid serving most of Virginia to direct big electricity users to switch to their own backup generators before resorting to rolling blackouts. In Northern Virginia, records show six diesel units in Ashburn ran for most of a day under that authority.

Paragraph B of Department of Energy Order No. 202-26-45 authorized PJM Interconnection, starting Sept. 17, to direct backup generation resources "whether auxiliary, standby, directly-connected, battery storage, or other, and whether synchronized or not to the bulk power system" to operate "as a last resort before declaring an EEA 3 (i.e., before firm load interruption) or during an EEA 3." Paragraph C says the order "requires the operation" of those backup resources and allows time for an orderly ramp-down afterward.

Why the grid wanted it

PJM asked for the authority in its Sept. 16 application. It said having large loads run on their own generation "could help the RTO avoid residential load shed at EEA level 3." It asked DOE to allow "use of backup generation by large loads notwithstanding any applicable environmental limitations under federal, state, or local law or regulation." PJM also asked that the order make clear it could call on transmission owners to work with local distribution utilities "to take lawful actions" to bring the backup resources online.

The order granted those requests, with conditions.

What ran in Northern Virginia

PJM's Exhibit A lists six diesel units in Ashburn, ZIP 20147, labeled VA1, VA2, VA3, VA5, VA6 and VA10, with nameplate ratings totaling about 98 megawatts, and a 30-megawatt diesel unit labeled CH1 in Gainesville, ZIP 20155. PJM's compliance report for Sept. 17 shows the Ashburn units ran 8 to 10 hours. CH1 is not listed on it.

The filings do not say who owns the units or what facilities they serve.

Air quality: what is and isn't known

For each Ashburn unit, Exhibit A lists the relaxed restriction as "Limitation on emergency engine operation." The Gainesville entry adds "fuel burn limitations." Those limits normally cap how long emergency engines may run outside true emergencies.

Under the order, hours, fuel and emissions during the emergency do not count toward rolling-average limits. Paragraph F still requires compliance with monitoring, reporting and recordkeeping "to the maximum extent practicable," and Paragraph J says the units must follow state, local and federal law once the order expires. Paragraph H lets DOE request more information about environmental impacts.

PJM's compliance report lists only run hours. It gives no figures for electricity generated, fuel burned, or emissions of nitrogen oxides, particulate matter or other pollutants. Without those numbers, the effect on local air quality during the event cannot be measured from the federal record. The Virginia Department of Environmental Quality issues air permits for stationary engines and would hold any permit-level records.

Noise

The federal filings say nothing about noise. Neither PJM nor DOE documents describe noise levels, enclosures or the distance from the Ashburn units to homes, and they do not say what time of day the units ran. Loudoun County's noise rules and any conditions in local permits would govern those questions.

Limits in the order

The order does not apply to backup generators "serving a critical reliability or backup need," including at hospitals, 911 call centers, water and wastewater plants, defense and homeland security sites, first-responder facilities, air traffic control and natural gas pipeline and gathering facilities. Backup units used under the order are not counted as capacity resources.

The authority was tied to emergency levels. It was a last resort before or during an Energy Emergency Alert Level 3, and the order expired after Sept. 18. PJM had declared an Energy Emergency Alert Level 1 for Sept. 17 and 18 and said it was forecast to be about 700 megawatts short of its reserve margin, with strain most acute in the BGE, Pepco and Dominion zones.

Precedent

The backup-generation provision follows a Jan. 22, 2026, letter from Energy Secretary Chris Wright to grid operators. PJM cited earlier 2026 orders, including ones in January, May, June, July and Sept. 1, that allowed similar dispatch.

Documents

The order, PJM's application, its supplemental letter and Exhibit A are posted on the Department of Energy's 202(c) page for Order No. 202-26-45 at energy.gov. PJM's daily compliance report for Sept. 17 is posted at pjm.com.

Loudoun County is a county in Northern Virginia. Its county seat is Leesburg.