Why do data centers have generators, and what are their air quality and regulatory implications?

Backup generators provide emergency power if the electric grid fails, so servers keep running and data isn’t lost. Generators are tested regularly (usually monthly) so operators know they will start reliably in an actual emergency.

Air quality permitting is significant. Under the federal Clean Air Act, large generator fleets can trigger New Source Review and Title V operating permit requirements, with a Prevention of Significant Deterioration construction permit required if the facility’s emissions exceed 250 tons per year of nitrogen oxides or carbon monoxide. Generators must burn ultra-low-sulfur diesel, and new engines are subject to EPA New Source Performance Standards.