As of April 2014, 16 U.S. states and the District of Columbia have deregulated electricity markets. Along with aforementioned Maryland and Texas, electricity deregulation is current in Connecticut, Delaware, Illinois, Maine, Massachusetts, Michigan, Montana, New Hampshire, New Jersey, New York, Ohio, Oregon, Pennsylvania, and Rhode Island. Seven additional U.S. states began the process of electricity deregulation but have suspended efforts: Arizona, Arkansas, California, Nevada, New Mexico, Virginia, and Wyoming.
Retailers Include: AEP Energy , APG&E Energy Solutions , Calpine Energy Solutions , Constellations NewEnergy, INC , Crius Energy , Direct Energy Services LLC , Dynegy , ENGIE Resources , Entrust Energy , IGS Energy , Just Energy , Liberty Power , Next Era Energy Services , Nordic Energy Services, LLC , NRG Energy INC , Source Energy , Spark Energy , Starion Energy , Stream Energy , Talen Energy , TransCanada Power Marketing LTD. 
Generally, the generation of electricity is unrelated to anything on your bill. Power plant companies generate electricity and sell it to utilities as well as retail electricity providers in deregulated areas. The electricity is then resold to you, the customer. Transmission and distribution is taken care of and charged to you by your utility, regardless of what company supplies the electricity. These charges are separate from the supply portion of your bill.