** Shares of U.S.-based solar company First Solar FSLR.O fall 11.6% to $220.73, their lowest level since October 2025

** BMO downgrades stock to "market perform" from "outperform"; cuts PT to $263 from $285, still a 5.62% upside to stock's last close

** Says Tesla TSLA.O CEO Elon Musk's plans to build massive solar panel manufacturing capacity of 100 GW per year could weigh on FSLR

** "..his (Musk) remarks during today's earnings call suggest to us that this is likely to become a bona fide effort in the next few quarters and may be an overhang on FSLR shares for some time" - BMO

** Brokerage notes that even if a portion of Tesla's planned capacity is available for third parties, it could negatively impact long-term module pricing

** 34 of 41 brokerages rate the stock "buy" or higher, 6 "hold" and 1 "sell" or lower; median PT is $284 - LSEG data

** Including session's moves, stock down about 15% YTD, after gaining 48.2% in 2025

(Reporting by Ragini Mathur in Bengaluru)

((Ragini.Mathur@thomsonreuters.com;))