Shares of Sunrun Inc. surged as much as 40% following updated guidance from the U.S. Treasury Department that solar projects under 1.5 megawatts may qualify for federal tax credits by spending 5% of project costs. This development has sparked a rally across the solar sector, with other companies such as Enphase Energy, First Solar, and SolarEdge Technologies also experiencing notable gains. Citi highlighted the positive impact of the Treasury's retroactivity news on solar stocks including TAN, RUN, CSIQ, FSLR, SEDG, and ENPH. GLJ Research upgraded Sunrun’s rating from sell to hold, citing the Treasury guidance as a major win for residential solar by preserving key tax credit provisions beyond 2025. The sector had faced setbacks earlier in the year due to the Build Back Better (BBB) legislation but has since rebounded, with some stocks rising between 150% and 400% from their lows. Options activity on Sunrun also reflected strong investor interest, with significant call purchases noted in March contracts.