Entergy Corporation, together with its subsidiaries, engages in the production and retail distribution of electricity in the United States. It generates, transmits, distributes, and sells electric power in portions of Arkansas, Louisiana, Mississippi, and Texas, including the City of New Orleans; and distributes natural gas. It also engages in the ownership of interests in non-nuclear power plants that sell electric power to wholesale customers, as well as provides decommissioning services to other nuclear power plant owners. It generates electricity through gas, nuclear, coal, hydro, and solar power sources. The company sells energy to retail power providers, utilities, electric power co-operatives, power trading organizations, and other power generation companies. The company's power plants have approximately 24,000 megawatts of electric generating capacity. It delivers electricity to 3 million utility customers in Arkansas, Louisiana, Mississippi, and Texas. Entergy Corporation was founded in 1913 and is headquartered in New Orleans, Louisiana.

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.

Atmos Energy Corporation, together with its subsidiaries, engages in the regulated natural gas distribution, and pipeline and storage businesses in the United States. It operates through two segments, Distribution, and Pipeline and Storage. The Distribution segment is involved in the regulated natural gas distribution and related sales operations in eight states. This segment distributes natural gas to approximately 3.3 million residential, commercial, public authority, and industrial customers; and owned 73,689 miles of underground distribution and transmission mains. The Pipeline and Storage segment engages in the pipeline and storage operations. This segment transports natural gas for third parties and manages five underground storage facilities in Texas; provides ancillary services customary to the pipeline industry, including parking arrangements, lending, and inventory sales; and owned 5,645 miles of gas transmission lines. Atmos Energy Corporation was founded in 1906 and is headquartered in Dallas, Texas.

NiSource Inc., an energy holding company, operates as a regulated natural gas and electric utility company in the United States. It operates in two segments, Gas Distribution Operations and Electric Operations. The company distributes natural gas to approximately 3.3 million customers through approximately 55,000 miles of distribution main pipeline and the associated individual customer service lines; and 1,000 miles of transmission main pipeline in northern Indiana, Ohio, Pennsylvania, Virginia, Kentucky, and Maryland. It also generates, transmits, and distributes electricity to approximately 0.5 million customers in various counties in the northern part of Indiana, as well as engages in wholesale electric and transmission transactions. It owns and operates coal-fired electric generating stations in Wheatfield and Michigan City; combined cycle gas turbine in West Terre Haute; natural gas generating units in Wheatfield; hydro generating plants in Carroll County and White County; wind generating units in White County, Indiana; and solar generating units in Jasper County and White County. The company was formerly known as NIPSCO Industries, Inc. and changed its name to NiSource Inc. in April 1999. NiSource Inc. was founded in 1847 and is headquartered in Merrillville, Indiana.

Black Hills Corporation, through its subsidiaries, operates as an electric and natural gas utility company in the United States. The company operates in two segments: Electric Utilities and Gas Utilities. The Electric Utilities segment generates, transmits, and distributes electricity to approximately 222,000 electric utility customers in Colorado, Montana, South Dakota, and Wyoming; and owns and operates 1,394 megawatts of generation capacity and 9,106 miles of electric transmission and distribution lines. The Gas Utilities segment distributes natural gas to approximately 1,116,000 natural gas utility customers in Arkansas, Colorado, Iowa, Kansas, Nebraska, and Wyoming; owns and operates 4,663 miles of intrastate gas transmission pipelines; 42,514 miles of gas distribution mains and service lines; seven natural gas storage sites; and approximately 50,000 horsepower of compression and 516 miles of gathering lines. It also constructs and maintains customer owned gas infrastructure facilities for gas transportation customers; and provides appliance repair services to residential utility customers, as well as electrical system construction services to large industrial customers. In addition, the company produces electric power through wind, natural gas, and coal-fired generating plants; and coal at its coal mine located near Gillette, Wyoming. Black Hills Corporation was incorporated in 1941 and is headquartered in Rapid City, South Dakota.

MGE Energy, Inc., through its subsidiaries, operates as a public utility holding company primarily in the United States. It operates through Regulated Electric Utility Operations; Regulated Gas Utility Operations; Nonregulated Energy Operations; Transmission Investments; and All Other segments. The company generates, purchases, and distributes electricity and natural gas in Wisconsin and Iowa; owns and leases electric generating capacity; and plans, constructs, operates, maintains, and expands transmission facilities to provide transmission power services. It generates electricity from coal-fired, gas-fired, and renewable energy sources. As of December 31, 2023, the company owned and operated 835 miles of overhead electric distribution lines; 1,330 miles of underground electric distribution cables; 49 substations with an installed capacity of 1.2 million kVA; and gas facilities, including 3,066 miles of distribution mains, as well as supplied electric service to approximately 163,000 customers. MGE Energy, Inc. founded in 2001 and is headquartered in Madison, Wisconsin.

Centuri Holdings, Inc. operates as a utility infrastructure services company in North America. It offers gas utility services, including maintenance, repair, installation, and replacement services for natural gas local distribution utility companies with focus on the modernization of infrastructure. The company also provides electric utility services comprising design, maintenance and repair, upgrade, and expansion services for transmission and distribution infrastructure. Its customers include electric, gas, and combination utility companies, as well as serves end markets, such as renewable energy and 5G datacom. The company was founded in 1909 and is headquartered in Phoenix, Arizona. Centuri Holdings, Inc. is a subsidiary of Southwest Gas Holdings, Inc.

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.