Key TakeawaysNRG Energy was the S&P 500's best-performing component Tuesday.Jefferies analysts upgraded their rating for the stock to "buy" and raised their price target, saying “investors are sleeping” on the energy company.NRG Energy and other utilities companies have seen their shares rise this year on expectations they could benefit from growing energy demand for data centers to support AI. NRG Energy (NRG) was the S&P 500’s best-performing constituent Tuesday after Jefferies analysts upgraded the stock ...