EMFAC2025 Version Updates

EMFAC2025 Version Updates#

This appendix summarizes changes made to EMFAC2025 since version 2.0.0 (May 2025). Each update includes a brief description and its expected impact on model outputs.

EMFAC2025 v2.1.0, March 2026#

  • The Advanced Clean Cars II, Advanced Clean Trucks (ACT), Zero-Emission Airport Shuttle, Heavy-Duty Vehicle and Engine Emission Warranty and Maintenance Provisions (Warranty Phase 1), and Heavy-Duty Omnibus (Omnibus) regulations were removed in response to unlawful resolutions, which purported to disapprove U.S. EPA’s prior actions to grant California waivers for these rules. As a result, emissions are higher for affected vehicle categories due to the absence of stricter emission standards and the continued operation of higher-emitting vehicles.

  • Several minor bugs were corrected to improve calculation accuracy and model stability.

EMFAC2025 v2.1.1, May 2026#

  • Zero-Emission Vehicle (ZEV) population estimates for light-duty vehicles (2023 to 2050) were updated to align with California Energy Commission (CEC) Integrated Energy Policy Report (IEPR) 2025 forecasts. The previous version underestimated ZEV counts and did not match the CEC projections described in Section 4.5. The update increases ZEV populations for LDA, LDT1, LDT2, and MDV, resulting in lower emissions for these categories due to a higher share of zero-emission vehicles in the fleet.

  • Renewable gasoline was introduced as a fuel component for gasoline and plug-in hybrid vehicles, based on the Low Carbon Fuel Standard (LCFS) 2025 Q3 Quarterly Report. This change produces a negligible reduction (less than 0.01%) in greenhouse gas (GHG) emissions for all gasoline vehicles.

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