Lawmakers debate how to regulate data centers’ diesel backup generators

There are over 9,000 backup generators that can supply emergency power to Northern Virginia data centers, some of which run on diesel and emit toxins. The use of these generators became a flashpoint in communities concerned about the health impacts of the emissions and fueled legislation in this year’s General Assembly session, as new research sheds more light on how much pollution the generators produce. 

The Department of Environmental Quality limits when the diesel generators deemed Tier II can run, which is mostly in emergency situations and during regular testing. But lawmakers who represent areas where hundreds of data centers are concentrated said the emissions from the generators, even just during the testing hours each month, are harmful to the health of surrounding communities.

House Bill 507, sponsored by Del. John McAuliff, D-Fauquier, has been amended to direct the Virginia Department of Environmental Quality to not issue air permits to data centers with generators below the emissions quality of the Tier IV generators, starting with applications after July 2026. 

His bill originally required data centers to utilize battery storage as the main backup source and created siting and notification requirements for the generators – but those aspects of the bill have now been removed.

“I will note it’s probably not the final step toward making sure that we have the best possible tech out there and being used, and those generators are being used in the right way for our communities, but it is a very good first step,” McAuliff said in a Feb. 11 committee.

The U.S. Department of Energy allowed data centers in PJM – the regional power grid – to run fully on generator power if they needed to during the frigid cold snap at the end of January, even if it meant going over their permitted emissions. A representative from PJM said no data centers in the Dominion Energy zone needed to kick over to backup power during the emergency order, including in Virginia.

Senate Bill 336 by Sen. Danica Roem, D-Manassas, has been reduced to requiring the State Corporation Commission conduct a study to review the impacts of prioritizing the use of Tier IV generators over Tier II ones. It instructs the commission to consider the environmental impacts as well as costs to data centers to retrofit their back power generation.

In its original version, the bill would have mandated that data centers invest more in pricier but less toxic Tier IV generators. 

“We do realize that in the event that we had the 200 some odd (data centers) in Loudoun, plus all the ones in Prince William, if they were running on generators at the same time, there’s not enough hospitals in the entire state that would be even close in league with that,” Roem said in a committee hearing for SB 336. “We are talking about a very specific issue dealing with a very specific industry because of the size and scope of the industry.”

HB1502 by Del. Elizabeth Guzman, D-Prince William, has also been amended to direct DEQ to conduct a one-year study of all standby generators run by commercial entities that are currently permitted to determine which pollutants are emitted – and how much.“We all know that standby generators produce many harmful pollutants. These pollutants have been associated with cardiovascular and respiratory diseases and emergency room visits for asthma, among other health effects,” Guzman said in committee.

SB 336 is now headed to the House while HB 507 and HB 1502 are waiting for final passage on the House floor to be sent to the Senate.

A recent study conducted by the VCU Institute for Sustainable Energy and Environment by Damian Pitt, Ivan Suen, and Ellie Plisko found toxins are being released into the localities where data centers with the diesel generators are concentrated. The study used data from emissions reports in 2023 and compared what the air emissions would be if the data centers would reach their permitted cap.

“Not that anyone thinks they’re all gonna all of a sudden hit 100% of their permits, but it gives you a sense of what is currently allowed,” Pitt said. “It’s pretty shocking, the degree of total emissions exposure that would result in those clustered areas if they were to actually admit their permitted amounts.”

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