Data centers could rely on arrays of massive generators to avoid power outages across Pennsylvania and a dozen other states during this week’s heat wave.

For the third time in less than three weeks, the U.S. Department of Energy authorized PJM Interconnection, the country’s largest grid operator serving 67 million people, to order data centers to rely on their backup generators rather than draw power from the grid as a last resort to maintain grid reliability as temperatures exceed 90 degrees. The emergency order, issued by U.S. Secretary of Energy Chris Wright, went into effect Tuesday at 11:59 p.m. and remains in place through July 21 at 11:59 p.m. In addition to allowing data centers and other large-load users to tap their backup generators for power, the order waives environmental permitting restrictions for a list of power generators to maintain grid reliability, including a natural gas power plant in Hazleton.

“PJM also seeks to unlock and deploy backup generation resources (whether auxiliary, standby, directly-connected, battery storage or other, and whether synchronized or not to the bulk-power system) at data centers (including, but not limited to, hyperscaler facilities), and at other large load industrial and commercial customer sites as another tool to mitigate any undue risk to the bulk-power system,” Wright wrote in the order Tuesday. “PJM states the employment of this backup generation is expected to reduce stress on the grid and permit orderly, safe, and secure operations during the hot weather conditions.”

PJM applied for the authorization on Monday — the third time it has done so since late June. PJM is a regional transmission organization encompassing all or parts of Delaware, Illinois, Indiana, Kentucky, Maryland, Michigan, New Jersey, North Carolina, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia and Washington, D.C.

In an application addressed to Wright, PJM Chief Operating Officer Frederick S. Bresler pointed to forecasted temperatures in the mid-to-upper 90s across its territory and cited regional capacity deficiencies and/or transmission constraints.

“The forecasted demand raises a significant risk of emergency conditions that could jeopardize electric reliability and public safety,” Bresler wrote, later adding, “Absent such an order, there is a risk that residences, hospitals, military facilities, water treatment plants, and other critical facilities may lose electric service to all or parts of their facilities due to the lack of adequate generation or transmission.”

In Northeast Pennsylvania, the orders have already begun to shift how municipalities and opponents view data center campuses and the hundreds of diesel generators they would use to maintain round-the-clock operations to sustain uses like artificial intelligence and cloud computing.

With intense electricity demands, data centers are outpacing the development of new power plants, straining the available electricity on the grid. PJM recently reported new data centers and expansions of existing sites can be developed two to three times faster than many of the electric generation technologies needed to serve them.

Locally proposed campuses often range from hundreds of megawatts to more than a gigawatt of power, and their on-site generators have to provide just as much power, rivaling or even exceeding the amount of electricity produced at local power plants. Municipalities have so far regulated the developments on the assumption they would run their generators only during power outages and for routine testing and maintenance. However, if those generators become grid reliability resources, it could increase how often they run, amounting to more air pollution and noise impacts on surrounding communities.

For one hyperscale data center campus alone — the proposed 14-building Wildcat Ridge Data Center Campus and its 588 diesel generators in Archbald — countywide health impacts could range from $3.3 million to $124 million, depending on the generators’ emissions controls and runtime, according to a Harvard University environmental health scientist who testified about the project this month and recently spoke with The Times-Tribune. The difference of 16 hours versus 100 hours of runtime alone in a less stringent generator shifts those health impacts from as low as $14 million to a projected $124 million, according the screening-level air quality and public health assessment from Michael Cork, Ph.D., of EmPower Analytics Group.

On Monday, an acoustics expert hired by Archbald testified that the noise from those 588 generators would significantly impact residents when run during an emergency, peaking at 16 times louder than background noise at two of the closest residences.

PJM initially received approval to tap data centers’ backup power from June 30 at 11:59 p.m. through July 3 at 11:59 p.m. during the previous heat wave. It then requested and received an extension through July 7.

Although PJM hit a record all-time demand on July 2 with an estimated 168,158 megawatts, surpassing a record set in August 2006 by nearly 3,000 megawatts, it did not ultimately resort to ordering data centers to use backup power.

By comparison, the Lackawanna Energy Center natural gas-fired power plant in Jessup produces 1,485 megawatts, and the Susquehanna Steam Electric Station nuclear power plant in Berwick produces 2,245 megawatts.

As of 5 p.m. Wednesday, PJM had not called on data centers for backup power.