This analysis provides first-ever assessment of the extent to which renewable energy is crossing state borders to be used to meet renewable portfolio standard (RPS) requirements. Two primary methods for data collection are Renewable Energy Certificate (REC) tracking and power flow estimates. Data from regional REC tracking systems, state agencies, and utility compliance reports help understand how cross-state transactions have been used to meet RPS compliance. Data on regional renewable energy flow use generator-specific information primarily sourced from EIA, SNL Energy, and FERC Form 1 filings. The renewable energy examined through this method may or may not have actually been used to meet RPS compliance.