** Shares of utility co Vistra Corp VST.N up 5.1% at $166.50 premarket

** Co swings to a Q1 profit from a loss a year ago, driven by rising power demand and prices

** Posts Q1 net income of $980 mln, compared with a loss of $317 mln a year earlier

** Co's Texas and East segments see adjusted core profit rise more than 19% and 55%, respectively

** Vistra reaffirms its outlook for 2026 adjusted core profit from continuing operations to be in the range of $6.8 bln to $7.6 bln

** As of last close, VST stock down 1.8% YTD