Microsoft Leesburg data center, Loudoun County, Virginia

Microsoft's Leesburg data center is one of the buildings that make Loudoun County, Virginia the densest concentration of them in the world, operating at about 180 megawatts. As of March 1, 2026 the county counted about 233 data center buildings built or under construction, roughly 56.5 million square feet, and the taxes they pay came to $1.2 billion in the 2026 financial year, 39 percent of the whole county budget. Dominion has proposed raising residential electricity rates 14 percent in 2026, citing data center growth and AI demand.

What people who live among them complain about is noise and diesel fumes. After a power failure on July 16, 2026 set backup generators running across the county, one homeowner said: "I always know when they're running their diesel generators because it irritates my throat and my lungs, and I've even woken up at night." County chair Phyllis Randall was due to meet residents living near the data centers that week. In Sterling, Greg Pirio measured 60 decibels at his property line while a Vantage Data Centers site ran its generators for about 24 hours after that same failure, and left home: "I had to go to my daughter's house because it was hurting my lungs." Virginia DEQ director Michael Rolband said the agency had no power to stop emergency generators running under the rules as they stand, and Sterling district supervisor Koran Saines said he would put an initiative to the board directing county staff to find a way to regulate them.

The county's zoning ordinance caps sound at 55 dBA at the property line of a residential property, and every data center must file a noise assessment before building and another within a year of occupancy. The rules say nothing about tonal or low frequency noise, and the language to cover it is not expected until amendments to the comprehensive plan and zoning ordinance in spring or summer 2027. Most of the backup diesels in the county are still Tier 2 units, some retrofitted with filters, and from July 1, 2026 Virginia requires Tier 4 equivalent emissions standards only for new or modified generators at data center sites.