GenOn Energy, Inc. (GenOn) is a wholesale generator with approximately 23,700 mega-watts of net electric generating capacity located near metropolitan load centers in the PJM Interconnection, LLC (PJM), Midwest Independent Transmission System Operator (MISO), Northeast and Southeast regions, and California. It also operates integrated asset management and trading operations. Its customers are independent system operators (ISOs), regional transmission organizations (RTOs) and investor-owned utilities. During the year ended December 31, 2011, approximately 42% and 37% of its realized gross margin during 2011 was attributable to its Eastern PJM and Western PJM/MISO operating segments, respectively. During 2011, in addition, approximately 51% of its realized gross margin was attributable to contracted and capacity energy services.