Vistra gains, company to join Dow Jones Utility Average

** Shares of utility firm Vistra VST up 1.1% at $120.77 after the bell

** Company to replace AES AES in the Dow Jones Utility Average (.DJU)

** Vistra has been the top performer in the S&P 500 SPX index in 2024, with higher YTD gains than chipmaker Nvidia NVDA

** Company is banking on rising demand for clean and sustainable power from AI data centers

** Up to last close, stock has more than tripled, YTD