EPA’s New Turbine Rules Provide Air Permitting Relief for Data Centers

On January 15, 2026, EPA published a New Source Performance Standard (NSPS) for stationary combustion and gas turbines in the Federal Register (91 Fed.Reg. 1910). This final rule significantly reduces permit obligations for certain turbines used in data center applications. The rule applies to turbines that either meet a yet-to-be-promulgated new definition of “mobile source turbine” or if permitted as a “temporary” turbine.

For stationary combustion turbines, the rule categorizes sources based upon size, utilization rates, design efficiency, and fuel type and requires combustion controls for NOX with additional selective catalytic reduction for large combustion turbines with high utilization rates.

In addition to these controls, EPA exempted from the Title V major source permitting program certain “low use” combustion turbines that do not independently qualify as major sources or are not located at major sources.  This exemption would apply to Small, Medium, and Large “low use” subcategories. Permitting these sources would now fall to the States non-major permitting programs. To further streamline permits for these sources, EPA has suggested that States use general permits or permits by rule. It is not clear, however, how combustion turbines that meet any of the “low use” categories will also meet the intense power generation needs of data centers.

EPA also added a subcategory that covers small- and medium-sized combustion turbines that are used in “temporary” applications. The temporary designation applies to combustion turbines with rated capacity of up to 850 MMBtu/hour used for less than 24 months. However, a temporary turbine cannot be replaced with another temporary turbine to circumvent the permitting requirement.

Use of “temporary” turbines in data center applications has drawn criticism where no alternate or replacement power source is apparent. At least one Federal Clean Air Act citizen suit has been filed against a data center operator, which relied on the “temporary” status as an exclusion from permit application and emission control requirements. (NAACP et.al., v. X.AI Corp. and MZX Tech LLC, No: 3;26-cv-74-MPM-JMV, 4.14.26, pending in U.S. District Court for the Northern District of Mississippi.) Notably, the U.S. Department of Justice has indicated that it may intervene in the suit or file amicus to support the United States government’s policy to “sustain and enhance America’s global AI dominance.”

Of interest to data centers using temporary turbines to provide power, the Federal Register notice indicates that the EPA believes that combustion turbines may qualify as “a kind of internal combustion engine” that could be regulated as nonroad engines (i.e., mobile sources) under Title II of the Act.” (See discussion at 91 FR 1926). However, the current definition of nonroad engine does not identify combustion turbines as a nonroad engine or mobile source. If EPA adopts a rule that confirms combustion turbines as mobile sources, this would exempt such turbines from the new source review permitting requirements of the Act because it will no longer be considered part of the stationary source.

In the final rule, EPA creates a conditional exclusion for temporary turbines.  The exclusion removes combustion turbines from the definition of  “stationary combustion turbines”—but only if the turbine meets the definition of nonroad engine and is certified to meet emission standards adopted under Title II of the Act.  According to the EPA, this exclusion will become effective if EPA adopts nonroad emission standards and certification requirements for portable combustion turbines. At that time, the manufacturer of combustion turbines will be subject to the Title II requirements for mobile sources, including obtaining certificates of conformity.

EPA recognized that this “mobile source” exclusion will require a separate rulemaking. Large power supply project developers and users who will rely on gas turbines should engage with EPA to clarify the path forward for this exclusion.

This publication is intended for general informational purposes only and does not constitute legal advice or a solicitation to provide legal services. The information in this publication is not intended to create, and receipt of it does not constitute, a lawyer-client relationship. Readers should not act upon this information without seeking professional legal counsel. The views and opinions expressed herein represent those of the individual author(s) only and are not necessarily the views of Clark Hill PLC or Clark Hill Solicitors LLP. Although we attempt to ensure that postings on our website are complete, accurate, and up to date, we assume no responsibility for their completeness, accuracy, or timeliness.