Enlarge (credit: TVA.gov) In the United States, electricity generation accounts for nearly 30% of our carbon emissions. Some states have responded to that by setting aggressive renewable energy standards; others are hoping to see coal propped up even as its economics get worse. Complicating matters further is the fact that many regional grids are integrated, meaning power generated in one location may be exported and used in a different state entirely. Tracking these electricity exports is critical for understanding how to lower our national carbon emissions.