Shares of NRG Energy Inc. /zigman2/quotes/208308731/composite NRG +0.65% shed 3.7% in premarket trading Friday, after the electricity and natural gas company said it will pay $3.625 billion in cash to buy U.K.-based Centrica PLC's /zigman2/quotes/205228367/delayed UK:CNA +0.61% /zigman2/quotes/203752788/composite CPYYY +0.82% North American subsidiary, Direct Energy. NRG said the deal, which is expected to close by the end of 2020, is expected to create $300 million in annual synergies. Direct Energy is a retail provider of electricity, natural gas and home and energy-related products and services with operations in all 50 U.S. states and in 6 provinces in Canada. "Direct Energy's significant East footprint provides better balance within NRG's existing portfolio while also providing NRG the ability to expand its successful capital-light renewable [Power Purchase Agreement] strategy outside of Texas," NRG said in a statement. NRG's stock has declined 16.4% year to date through Thursday and Centrica's U.S.-listed shares have tumbled 58.0%, while the SPDR Utilities Select Sector ETF /zigman2/quotes/206645117/composite XLU +0.81% has lost 6.1% and the S&P 500 /zigman2/quotes/210599714/realtime SPX +0.36% has edged up 0.2%.