Vistra Energy is a holding company operating an integrated power business in Texas. Through its Luminant and TXU Energy Retail Company LLC (TXU Energy) subsidiaries, Co. is engaged in electricity market activities, including electricity generation, wholesale energy sales and purchases, commodity risk management activities, and retail sales of electricity. Co. operates solely in the Electric Reliability Council of Texas, Inc. (ERCOT) electricity market. ERCOT is an independent system operator and the regional coordinator of various electricity systems within Texas. Co. segments are: Wholesale Generation, consisting mainly of Luminant, and Retail Electricity, consisting mainly of TXU Energy.