Under the GHG Protocol Corporate Accounting Standard, quantifying indirect greenhouse gas emissions from purchased electricity requires the application of robust emission factors. For U.S. operations, the EPA Emissions & Generation Resource Integrated Database (eGRID) is the universally mandated standard for location-based Scope 2 accounting.
Core eGRID Accounting Rules
eGRID organizes the contiguous United States into 26 distinct subregions reflecting contiguous electric transmission control boundaries. Using national average emission factors is explicitly disallowed under GHG Protocol Scope 2 Guidance when subregion factors are available.
1. Subregional Grid Carbon Intensity Variances
Emission factors vary significantly based on generation mix:
- CAMX (WECC California): Lower carbon intensity (~450 lbs CO₂e/MWh) driven by extensive solar, hydro, and geothermal resources.
- MROE (MRO East / Midwest): High carbon intensity (~1,100+ lbs CO₂e/MWh) due to baseload coal and natural gas generation.
- Transmission and Distribution (T&D) Losses: Reporting entities must account for grid line losses (typically 4.5% to 5.2%) under Scope 3 Category 3.
Compute Audit-Ready Scope 2 Emissions
Input facility electricity consumption by U.S. state and eGRID subregion to compute verifiable Scope 2 inventories.
2. Standards & Authoritative Data
- U.S. EPA: Emissions & Generation Resource Integrated Database (eGRID) Technical Support Document.
- WRI & WBCSD: GHG Protocol Scope 2 Guidance (Amendment to the Corporate Standard).
SCOPE 2 & POWER ACCOUNTING:
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