Two pieces of legislation expanding the sales tax exemption were enacted in May 2009. H.B. 1171 added residential wind energy equipment as eligible for this incentive. Residential wind energy equipment is equipment installed on a residential property that uses wind energy to generate electricity for use in a residential structure on that property. S.B. 621 revised the definition of solar energy equipment to include systems that supply electricity to the grid (e.g., through a net metering agreement). The amendments contained in both laws took effect July 1, 2009.