Wind power has the potential to reduce emissions associated with conventional electricity generation. Using detailed, systemic hourly data of wind generation and emissions from plants in ERCOT (Texas), we empirically estimate the SO2, NOx and CO2 emissions offset by wind generation. Our estimation strategy implicitly captures both the marginal unit of generation displaced by wind on the electrical grid, and the marginal emissions reduction from that displaced unit. Our results also reveal substantial variation in emissions reductions, which appear to be strongly driven by differences in the generation mix. The environmental benefits from emissions reductions in ERCOT fail to cover government subsidies for wind generation.