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.
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.
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.
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.
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'.
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).
Known gotchas
CAMX is the correct subregion code for the California/CAISO area; SRCA is not a current eGRID subregion code and will return no results.
Some plants physically located outside California (e.g., in Utah) are assigned to CAMX based on their balancing authority, not their geographic state — eGRID subregions follow power flows, not state borders.
Power Profiler assignment depends on the utility supplying power, not just the ZIP code; locations served by a non-CAISO utility may map to a different subregion even within California.
Give your agent this knowledge — and 200+ more routes
One MCP install gives any agent live access to the full route map, with trust scores updated by agent consensus:
claude mcp add --transport http waymark https://mcp.waymark.network/mcp