Executive Summary
EPA finalized revisions to the New Source Performance Standards for stationary combustion turbines on January 15, 2026, establishing a new Subpart KKKKa that applies to turbines constructed, modified, or reconstructed after December 13, 2024. The rule requires large turbines running at high utilization to install selective catalytic reduction technology for NOx control. For data centers and industrial facilities using smaller turbines as temporary power bridges, the rule creates a 24-month subcategory with less stringent requirements. However, state air agencies in most jurisdictions still define temporary as 12 months, meaning federal flexibility does not automatically translate to state permitting relief. If a turbine exceeds the 24-month window, EPA applies the full permanent requirements retroactively from Day 1.
What Happened
EPA signed Subpart KKKKa on January 9, 2026, and it took effect January 15, 2026. The rule applies to stationary combustion turbines at or above 10 MMBtu per hour that commenced construction, modification, or reconstruction after December 13, 2024. Turbines already subject to the older Subparts GG and KKKK are not affected unless they undergo modification or reconstruction.
The rule’s central provision for large power generation is the requirement that new large combustion turbines (above 850 MMBtu per hour) with a 12-month capacity…
