** Shares of some solar companies rise premarket
** SunRun RUN.O up 2.8%, seen as "biggest beneficiary" by Jefferies; First Solar FSLR.O jumps 3% to $205.99
** Canadian Solar CSIQ.O, Enphase ENPH.O, Complete Solaria SPWR.O gain 1%-1.8%
** Treasury on Friday unveiled new federal tax subsidy rules for how solar and wind projects
** Utility projects need "substantial and continuous" work for credits; small sub-1.5MW projects keep 5% "safe harbor" provision
** Changes were "milder than what many in the wind and solar industries had feared" - Raymond James
** Jefferies says rules extend the runway on tax credits for most wind/solar developers through 2030
** Expects "very real relief rally" for solar equities after regulatory clarity
(Reporting by Vallari Srivastava in Bengaluru)
((Srivastava.Vallari@thomsonreuters.com;))