Ashburn, Virginia, sits at the center of the nation's data center corridor. Diesel generators at a Digital Realty facility fired up over the July 4 weekend when temperatures climbed sharply.

Thick smoke rose above the ACC9 building, one of many facilities grouped in Ashburn and surrounding towns, based on video and images from July 3 reviewed by Business Insider. The operator explained the generators started as part of a PJM Interconnection initiative designed to cut demand on the grid at moments of highest usage.

Billions of dollars have flowed recently into expanding data centers across the country along with new power plants and transmission infrastructure. A Business Insider review showed 176 fresh data centers received permits in 2025, a group that could draw enough electricity to supply millions of residences.

The expanding presence of these facilities has sparked discussion over their contribution to higher energy prices. It has also raised concerns about pollution from fossil fuel backup systems, especially on hot days such as July 3 when Ashburn reached 102 degrees.

"We are essentially making routine the use of outdated power sources to keep the grid stable," said Elena Schlossberg, an activist based in northern Virginia. "Diesel fuel represents exactly that approach."

Emergency measures avoided

Data centers represent only about 5 percent of participants in PJM demand response efforts, according to data from the grid manager that oversees electricity for roughly one fifth of the U.S. population. These programs pay large users to lower consumption when the system faces peak strain.

Manufacturers make up 43 percent of demand response capacity across the PJM region. In places like Ashburn the biggest consumers include data centers operated by Amazon, Microsoft, and Equinix.

The Digital Realty site holds permits for 20 Caterpillar diesel units, each rated above 2 megawatts. The company declined to specify how many operated on July 3 yet noted permit rules limit total runtime.

A PJM summary indicated roughly 3.25 gigawatts of backup capacity ran beyond normal bounds during the extended heat spell covering the holiday weekend. Overall the demand response measures, including the ACC9 enrollment, prevented the need for stronger actions such as mandatory generator activation orders.

Local resident Bobby Chahal captured images of smoke rising from ACC9 while traveling through Ashburn on July 3 and recalled similar events the previous summer. He added that his power bills increased this year despite unchanged usage.

Data center projects have boosted local tax revenue in several communities. Collections tied to a large Meta facility in Louisiana funded teacher bonuses, while Loudoun County, home to Ashburn, received 875 million dollars from such sites in fiscal 2024, lowering average household tax burdens.

Nevertheless residents near these installations in northern Virginia report that noise and exhaust have reduced living standards and affected home values.

The continued construction, Chahal noted, "gives Ashburn an increasingly industrial and worn appearance."