Look up EPA eGRID emission factors for California (CAMX subregion)

Steps

1. Identify that California's primary eGRID subregion is CAMX (WECC California), which corresponds to the CAISO balancing authority area; do not use the legacy code SRCA.
2. Download the latest eGRID summary tables from https://www.epa.gov/egrid/summary-data; Table 1 (Subregion Output Emission Rates) lists CO2, CH4, and N2O rates per MWh for CAMX.
3. For ZIP-code-level subregion confirmation, use the EPA Power Profiler tool at https://www.epa.gov/egrid/power-profiler; enter the ZIP code and electric service provider to resolve the exact subregion when a location straddles multiple areas.
4. Apply the CAMX output emission rates (in lb/MWh) to your electricity consumption data; convert to metric tonnes CO2e using standard unit conversions as needed.
5. For programmatic lookup, download the full eGRID data workbook from the Detailed Data page and filter the SUBRGN worksheet for the row where SRABB equals 'CAMX'.
6. Re-download eGRID data annually as EPA updates it each year with a roughly two-year data lag (e.g., eGRID2022 data was published in January 2024).