Low electricity prices are making it less profitable to be a power plant operator. Companies that sell electricity to utilities, such as Dynegy Corp., Calpine Corp and NRG Energy Inc., reported slim profits or losses in the third quarter compared to the same period a year ago, as they continue to be battered by wholesale power prices that have fallen in recent years along with prices for natural gas. Average wholesale electricity prices have dropped 15% this year to $29.70 a megawatt-hour, according to a Wall Street Journal analysis of power market data from the Energy Department. That is 43% below the 2014 average. On Friday, NRG reported a quarterly profit of $393 million, compared to $67 million a year earlier. After adjusting for a $266 million increase from asset sales and other one-time […]