American Electric Power Company, Inc., an electric public utility holding company, engages in the generation, transmission, and distribution of electricity for sale to retail and wholesale customers in the United States. It operates through Vertically Integrated Utilities, Transmission and Distribution Utilities, AEP Transmission Holdco, and Generation & Marketing segments. The company generates electricity using coal and lignite, natural gas, renewable, nuclear, hydro, solar, wind, and other energy sources. It also supplies and markets electric power at wholesale to other electric utility companies, rural electric cooperatives, municipalities, and other market participants. American Electric Power Company, Inc. was incorporated in 1906 and is headquartered in Columbus, Ohio.

Xcel Energy Inc., through its subsidiaries, engages in the generation, purchasing, transmission, distribution, and sale of electricity. It operates through Regulated Electric Utility, Regulated Natural Gas Utility, and All Other segments. The company generates electricity through wind, nuclear, hydroelectric, biomass, and solar energy sources, as well as coal, natural gas, oil, wood, and refuse-derived fuels. It also purchases, transports, distributes, and sells natural gas to retail customers, as well as transports customer-owned natural gas. In addition, the company develops and leases natural gas pipelines, and storage and compression facilities; and invests in rental housing projects and nonregulated assets, as well as procures equipment for the construction of renewable generation facilities. It serves residential, commercial, and industrial customers in the portions of Colorado, Michigan, Minnesota, New Mexico, North Dakota, South Dakota, Texas, and Wisconsin. The company was incorporated in 1909 and is headquartered in Minneapolis, Minnesota.

WEC Energy Group, Inc., through its subsidiaries, provides regulated natural gas and electricity, and renewable and nonregulated renewable energy services in the United States. It operates through Wisconsin, Illinois, Other States, Electric Transmission, and Non-Utility Energy Infrastructure segments. The company generates and distributes electricity from coal, natural gas, oil, and nuclear, as well as renewable energy resources, including wind, solar, hydroelectric, and biomass; and distributes and transports natural gas. It also owns, maintains, monitors, and operates electric transmission systems; and generates, distributes, and sells steam. As of December 31, 2023, the company operated approximately 35,500 miles of overhead distribution lines and 36,500 miles of underground distribution cables, as well as 430 electric distribution substations and 523,700 line transformers; approximately 46,400 miles of natural gas distribution mains; 1,700 miles of natural gas transmission mains; 2.4 million natural gas lateral services; 490 natural gas distribution and transmission gate stations; and 69.3 billion cubic feet of working gas capacities in underground natural gas storage fields. The company was formerly known as Wisconsin Energy Corporation and changed its name to WEC Energy Group, Inc. in June 2015. WEC Energy Group, Inc. was founded in 1896 and is headquartered in Milwaukee, Wisconsin.

Ameren Corporation, together with its subsidiaries, operates as a public utility holding company in the United States. The company operates through four segments: Ameren Missouri, Ameren Illinois Electric Distribution, Ameren Illinois Natural Gas, and Ameren Transmission. It engages in the rate-regulated electric generation, transmission, and distribution activities; and rate-regulated natural gas distribution business. In addition, the company generates electricity through coal, nuclear, and natural gas, as well as renewable sources, such as hydroelectric, wind, methane gas, and solar. It serves residential, commercial, and industrial customers. The company was founded in 1881 and is headquartered in Saint Louis, Missouri.

CenterPoint Energy, Inc. operates as a public utility holding company in the United States. The company operates through two segments, Electric and Natural Gas. The Electric segment includes electric transmission and distribution services to electric customers and electric generation assets, as well as optimizes assets in the wholesale power market. The Natural Gas segment engages in the intrastate natural gas sales, and natural gas transportation and distribution for residential, commercial, industrial and institutional customers in Indiana, Louisiana, Minnesota, Mississippi, Ohio, and Texas; permanent pipeline connections through interconnects with various interstate and intrastate pipeline companies; and provides maintenance and repair services of home appliances to customers in Minnesota and home repair protection plans to natural gas customers in Indiana, Mississippi, Ohio, and Texas through a third party. It serves approximately 2,534,730 metered customers; owned 348 substations with transformer capacity of 79,719 megavolt amperes; and owned and operated 217 miles of intrastate pipeline in Louisiana and Texas. The company was founded in 1866 and is headquartered in Houston, Texas.

Alliant Energy Corporation operates as a utility holding company that provides regulated electricity and natural gas services in the United States. It operates in three segments: Utility Electric Operations, Utility Gas Operations, and Utility Other. The company, through its subsidiary, Interstate Power and Light Company (IPL), primarily generates and distributes electricity, and distributes and transports natural gas to retail customers in Iowa; sells electricity to wholesale customers in Minnesota, Illinois, and Iowa; and generates and distributes steam in Cedar Rapids, Iowa. Alliant Energy Corporation, through its other subsidiary, Wisconsin Power and Light Company (WPL), generates and distributes electricity, and distributes and transports natural gas to retail customers in Wisconsin; and sells electricity to wholesale customers in Wisconsin. It serves retail customers in the farming, agriculture, industrial manufacturing, chemical, packaging, and food industries, as well as wholesale customers comprising municipalities and rural electric cooperatives. In addition, the company owns and operates a short-line rail freight service in Iowa; a Mississippi River barge, rail, and truck freight terminal in Illinois; freight brokerage services; wind turbine blade recycling services; and a rail-served warehouse in Iowa. Further, it holds interests in a natural gas-fired electric generating unit near Sheboygan Falls, Wisconsin; and a wind farm located in Oklahoma. The company was formerly known as Interstate Energy Corp. and changed its name to Alliant Energy Corporation in May 1999. Alliant Energy Corporation was incorporated in 1981 and is headquartered in Madison, Wisconsin.

Avangrid, Inc., an energy services holding company, engages in the regulated energy transmission and distribution, and renewable energy generation businesses in the United States. The company operates through Networks and Renewables segments. It is involved in the generation, transmission, and distribution of electricity; and distribution, transportation, and sale of natural gas. In addition, the company operates renewable energy generation facilities primarily using onshore wind power, as well as solar, biomass, and thermal power. Further, it delivers natural gas and electricity to residential, commercial, and institutional customers through its regulated utilities in New York, Maine, Connecticut, and Massachusetts; and sells its output to investor-owned utilities, public utilities, and other credit-worthy entities, as well as generates and provides power and other services to federal and state agencies, institutional retail, and joint action agencies. Additionally, the company delivers thermal output to wholesale customers in the Western United States. It owns eight electric and natural gas utilities, serving 3.3 million customers in New York and New England, as well as owns and operates 9.3 gigawatts of electricity capacity primarily through wind power in 22 states. Avangrid, Inc. was incorporated in 1997 and is headquartered in Orange, Connecticut. The company operates as a subsidiary of Iberdrola, S.A.

Unitil Corporation, a public utility holding company, engages in the distribution of electricity and natural gas. It operates through two segments, Utility Electric Operations, Utility Gas Operations. The company distributes electricity in the southeastern seacoast and state capital regions of New Hampshire, and the greater Fitchburg area of north central Massachusetts; and distributes natural gas in southeastern New Hampshire and portions of southern and central Maine, including the city of Portland and the Lewiston-Auburn area, as well as electricity and natural gas in the greater Fitchburg area of north central Massachusetts. It also operates 86 miles of interstate underground natural gas transmission pipeline that provides interstate natural gas pipeline access and transportation services primarily in Maine and New Hampshire. In addition, the company provides real estate management services. It serves approximately 108,100 electric customers and 87,500 natural gas customers. Unitil Corporation was incorporated in 1984 and is headquartered in Hampton, New Hampshire.