Alliant Energy is a public utility holding company, engaged in providing regulated electric and natural gas service. The company's subsidiaries are: Interstate Power and Light Company, which is engaged principally in the generation and distribution of electricity and the distribution and transportation of natural gas to retail customers in select markets in Iowa; Wisconsin Power and Light Company, which is engaged principally in the generation and distribution of electricity and the distribution and transportation of natural gas to retail customers in select markets in Wisconsin; and Alliant Energy Finance, LLC, which manages a portfolio of wholly-owned subsidiaries and additional holdings.

Ameren is a public utility holding company. Through its subsidiary, Union Electric Company, the company operates a rate-regulated electric generation, transmission, and distribution business and a rate-regulated natural gas distribution business in Missouri. Through its subsidiary, Ameren Illinois Company, the company operates rate-regulated electric transmission, electric distribution, and natural gas distribution businesses in Illinois. Through its Ameren Transmission Company of Illinois subsidiary, the company operates a Federal Energy Regulatory Commission rate-regulated electric transmission business. The company also has other subsidiaries that conduct other activities, such as providing shared services.

Avista is a holding company. Through its subsidiaries, the company is primarily an electric and natural gas utility with certain other business ventures. The company has two reportable business segments: Avista Utilities, which provides electric distribution and transmission, and natural gas distribution services in parts of eastern Washington and northern Idaho, as well as natural gas distribution service in parts of northeastern and southwestern Oregon; and Alaska Electric Light and Power Company, which provides electric services in Juneau, AK. The company also has other businesses, including sheet metal fabrication, venture fund investments, real estate investments, as well as certain other investments.

CMS Energy is a holding company. The company has several subsidiaries, including: Consumers Energy Company, an electric and gas utility that serves individuals and businesses operating in the alternative energy, automotive, chemical, food, and metal products industries, as well as a group of other industries; CMS Enterprises Company, through its subsidiaries and equity investments, is engaged in domestic independent power production, including the development and operation of renewable generation, and the marketing of independent power production; and EnerBank USA, an industrial bank located in Utah that provides unsecured consumer installment loans, primarily for financing home improvements.

Exelon is a utility services holding company engaged in the generation, delivery and marketing of energy through Exelon Generation Company, LLC and the energy distribution and transmission businesses through Commonwealth Edison Company, PECO Energy Company, Baltimore Gas and Electric Company, Potomac Electric Power Company, Delmarva Power & Light Company and Atlantic City Electric Company. Through its business services subsidiary Exelon Business Services Company, LLC, the company provides its subsidiaries with a variety of support services.

NextEra Energy is a holding company, engaged in electric power and energy infrastructure. The company has two principal businesses, Florida Power & Light Company (FPL) and NextEra Energy Resources, LLC (NEER). FPL is a rate-regulated electric utility engaged primarily in the generation, transmission, distribution and sale of electric energy in Florida. FPL provides service to its electric customers through a transmission and distribution system that links its generation facilities to its customers. NEER, through its subsidiaries, owns, develops, constructs, manages and operates electric generation facilities in wholesale energy markets primarily in the United States and Canada.

Spark Energy is a holding company. Through its subsidiaries, the company is an independent retail energy services company. The company's segments include: Retail Electricity, where the company purchases electricity supply through physical and financial transactions with market counterparties and independent system operators and supplies electricity to residential and commercial consumers pursuant to fixed-price and variable-price contracts; and Retail Natural Gas, where the company purchases natural gas supply through physical and financial transactions with market counterparties and supplies natural gas to residential and commercial consumers pursuant to fixed-price and variable-price contracts.

WEC Energy Group is a holding company. Through its subsidiaries, the company provides regulated natural gas and electricity, and nonregulated renewable energy. The company's segments include: Wisconsin, which generates and distributes electric energy and provides retail natural gas distribution service; Illinois, which includes the natural gas utility operations; Electric Transmission, which owns, maintains, monitors, and operates electric transmission systems in Wisconsin, Michigan, Illinois, and Minnesota; and Non-Utility Energy Infrastructure, which owns and leases generating facilities to its Wisconsin Electric Power Company subsidiary and owns underground natural gas storage facilities in Michigan.

Xcel Energy is a regulated electric and natural gas delivery company which serves customers in mid-western and western states, including portions of Colorado, Michigan, Minnesota, New Mexico, North Dakota, South Dakota, Texas and Wisconsin. The company's reportable segments include: regulated electric utility, which generates, transmits and distributes electricity in Minnesota, Wisconsin, Michigan, North Dakota, South Dakota, Colorado, Texas and New Mexico; regulated natural gas utility, which transports, stores and distributes natural gas primarily in portions of Minnesota, Wisconsin, North Dakota, Michigan and Colorado; and other, which includes steam revenue and appliance repair services.