The AES Corporation is a Fortune 500 company that generates and distributes electrical power.[3] AES is headquartered in Arlington, Virginia, and is one of the world’s leading power companies, generating and distributing electric power in 15 countries[4] and employing 10,500 people worldwide.

American Electric Power (AEP) is a major investor-owned electric utility in the United States of America, delivering electricity to more than five million customers in 11 states. AEP ranks among the nation’s largest generators of electricity, owning nearly 38,000 megawatts of generating capacity in the U.S. AEP also owns the nation’s largest electricity transmission system, a nearly 39,000-mile (63,000 km) network that includes 765 kilovolt ultra-high voltage transmission lines, more than all other U.S. transmission systems combined.[4] AEP’s transmission system directly or indirectly serves about 10 percent of the electricity demand in the Eastern Interconnection, the interconnected transmission system that covers 38 eastern and central U.S. states and eastern Canada, and approximately 11 percent of the electricity demand in the Electric Reliability Council of Texas, the transmission system that covers much of Texas. AEP’s utility units operate as AEP Ohio, AEP Texas, Appalachian Power (in Virginia, West Virginia, and Tennessee), Indiana Michigan Power, Kentucky Power, Public Service Company of Oklahoma, and Southwestern Electric Power Company (in Arkansas, Louisiana and east Texas). AEP’s headquarters are in Columbus, Ohio. American Electric Power was the first utility to utilize 345 kV transmission lines which took place in 1953. The company ranked 185th on the 2018 Fortune 500 of the largest United States corporations by revenue.

CMS Energy (NYSE: CMS), based in Jackson, Michigan, is an energy company that is focused principally on utility operations in Michigan.[4] Its principal business is Consumers Energy, a public utility that provides electricity and natural gas to more than 6 million of Michigan’s 10 million residents.[5][6] Its non-utility businesses are focused primarily on domestic independent power production. Consumers Energy has operated since 1886.[7] CMS Enterprises’ primary businesses are independent power production and natural gas transmission.

Dominion Energy, Inc., commonly referred to as Dominion, is an American power and energy company headquartered in Richmond, Virginia that supplies electricity in parts of Virginia, North Carolina, and South Carolina and supplies natural gas to parts of West Virginia, Ohio, Pennsylvania, North Carolina, South Carolina, and Georgia. Dominion also has generation facilities in Indiana, Illinois, Connecticut, and Rhode Island.[7] The company acquired Questar gas in the Western United States, including parts of Utah and Wyoming, in September 2016.[8] In January 2019, Dominion Energy completed its acquisition of SCANA Corporation.

Edison International is a public utility holding company based in Rosemead, California. Its subsidiaries include Southern California Edison, and unregulated non-utility business assets Edison Energy. Edison’s roots trace back to Holt & Knupps, a company founded in 1886 as a provider of street lights in Visalia, California.

FirstEnergy Corp is an electric utility headquartered in Akron, Ohio. Its subsidiaries and affiliates are involved in the distribution, transmission, and generation of electricity, as well as energy management and other energy-related services. Its ten electric utility operating companies comprise one of the United States’ largest investor-owned utilities, based on serving 6 million customers within a 65,000-square-mile (170,000 km2) area of Ohio, Pennsylvania, West Virginia, Virginia, Maryland, New Jersey and New York.[4] Its generation subsidiaries control more than 16,000 megawatts of capacity, and its distribution lines span over 194,000 miles. In 2018, FirstEnergy ranked 219 on the Fortune 500 list of the largest public corporations in the United States by revenue.[5] In November 2016, FirstEnergy made the decision to exit the competitive power business, and become a fully regulated company.

NRG Energy, Inc. is a large American energy company, dual-headquartered in Princeton, New Jersey[4][5] and Houston, Texas.[3][6][7] It was formerly the wholesale arm of Northern States Power Company (NSP), which became Xcel Energy, but became independent in 2000. NRG Energy is involved in energy generation and retail electricity.[8] Their portfolio includes nuclear generation, coal generation, wind generation, utility scale generation, distributed solar generation, and oil generation.[9] NRG serves 2.9 million retail customers in Texas, Connecticut, Delaware, Illinois, Maryland, Massachusetts, New Jersey, New York, Pennsylvania, Ohio, and the District of Columbia.[4] NRG Energy has acquired eleven other energy companies, both generation and retail, that include Reliant Energy,[10] XOOM Energy,[11] Green Mountain Energy,[8] Stream Energy[12] and Cirro Energy.[13] As of 2018, they generate 23,000 MW of energy from 40 power plants across the country.[10] They incorporate a range of sales channels for retail customers, including call centers, direct sales, websites, brokers, and brick-and-mortar stores. Their wholesale generation services include plant operations, commercial operations, energy services, distributed generation services, and energy, procurement, and construction (EPC) services.

The PPL Corporation is an energy company headquartered in Allentown, Pennsylvania, United States. It currently controls about 8,000 megawatts of regulated electric generating capacity in the United States and delivers electricity to 10.5 million customers in Pennsylvania, Kentucky, and Great Britain. PPL is the parent to seven regulated utility companies in the U.S., and it also provides natural gas delivery service to 321,000 customers in Kentucky. PPL Electric Utilities (formerly known as PP&L and Pennsylvania Power and Light) is the PPL Corporation’s primary subsidiary. The majority of PPL’s power plants burn coal, oil, or natural gas. PPL also owns peaking plants, which require few operators and have a high profit margin due to their ability to rapidly come online when the price of electricity spikes. The company is publicly traded on the New York Stock Exchange.