More than three gigawatts of demand dropped from the PJM Interconnection at about 07:55 Eastern time on Wednesday. The loss represented roughly 3% of demand on the grid at that moment and produced a voltage disturbance detected from Washington to Chicago. PJM said reliability was not affected. [E1]
The event centered on Northern Virginia, the densest data-centre cluster in the United States. A network of power-quality sensors recorded flickering lights and appliance noise, and its operator said the wider system took about ten minutes to settle fully. PJM registered both the demand loss and a frequency change. [E1]
Data centers switching to batteries or generators are the leading explanation, not an established finding. Reuters reported that the cause remained unknown, and Dominion Energy had not publicly attributed the event by the edition bell. The distinction matters because a protection response, a transmission fault and coordinated backup transfer imply different remedies. [E1]
The mechanism is credible because it has happened before. A federal filing describes a 1.5-gigawatt data-centre load drop in Northern Virginia after a 2024 lightning strike and another episode involving roughly 40 facilities in 2025. A NERC incident review documents how simultaneous voltage-sensitive load reductions can raise frequency and voltage across the bulk system. [E2][E3]
Grid planning usually treats a data center as demand to be supplied. Fast backup systems give the same facility a second identity: a block of demand that can disappear within electrical cycles. Operators must then shed generation or absorb the imbalance quickly enough to control frequency and voltage. [E2][E3][E4]
Reliability bodies were already rewriting the rules around large loads. NERC concluded that existing standards and industry practices do not fully cover the risks created by emerging large loads. PJM has also proposed new ways to integrate facilities that can alter consumption during constrained hours. [E4][E5]
Wednesday’s record does not prove that artificial-intelligence campuses caused the disturbance, much less that every backup system presents the same risk. It does prove that a Northern Virginia event can erase power demand on the scale of several large generating units. Compute has become grid infrastructure even when it stops consuming. [E1][E3]