U.S. Grid Regions
The U.S. grid is divided into three major regions:
- The Eastern Interconnection, which operates in states east of the Rocky Mountains.
- The Western Interconnection, which covers the Pacific Ocean to the Rocky Mountain states.
- The Texas Interconnected system.
Within each of these regions are interconnected local electricity grids. With multiple ways for the power to flow from generation to load centers, this redundancy seeks to ensure minimal loss of service in case of local failures.
The North American Electric Reliability Corporation (NERC) is a not-for-profit international regulatory authority whose mission is to assure the effective and efficient reduction of risks to the reliability and security of the grid. NERC oversees six regional reliability entities and encompasses all the interconnected power systems of Canada and the contiguous United States, as well as a portion of Mexico.
For U.S. grid regions’ emission data, EPA provides recent and historic air emissions, including carbon dioxide (CO2), for U.S. portions of grid regions, States, and Puerto Rico.
EPA’s Emissions & Generation Resource Integrated Database (eGRID) is the preeminent source of air emission data for the U.S. electric power sector. eGRID is based on available data for all U.S. electricity generating plants that provide power to the electric grid and report data to the U.S. government.
eGRID is valuable to users seeking air emission data about the electric power sector in the United States. eGRID is typically used for greenhouse gas registries and inventories, carbon footprints, consumer information disclosure, emission inventories and standards, power market changes, and avoided emission estimate eGRID data are cited by many emission inventory and registry protocols, various emission calculation tools and applications, hundreds of academic papers, and consultants; it is used for many research applications and efforts.
eGRID annually updates its emission data and rates for each of its subregions. It also provides aggregated data by state, U.S. total, and by sets of electric grid boundaries, including NERC regions and eGRID subregions.
