NRG Energy (NRG) stock is among the most volatile stocks in the S&P 500 Utilities. On September 25, NRG Energy had an implied volatility of 24%—well below its 15-day average. In comparison, the Utilities Select Sector SDPR ETF’s (XLU) implied volatility was close to 13%. A stock’s implied volatility represents investors’ unease. Rising volatility is generally related to a fall in a stock’s price. The current volatility in NRG Energy stock has fallen. The stock even witnessed volatility levels close to 50% early this year.