Electric power generation, transmission, and distribution. This segment includes firms engaged in the generation, transmission, and distribution of electric power. Electric plants harness highly pressurized steam or some force of nature to spin the blades of a turbine, which is attached to an electric generator. Coal is the dominant fuel used to generate steam in electric power plants, followed by natural gas, petroleum, nuclear power, and other energy sources. Hydroelectric generators are powered by the release of the tremendous pressure of water existing at the bottom of a dam or near a waterfall. Scientists also are conducting considerable research into renewable sources of electric power—including geothermal, wind, and solar energy.

Natural gas distribution. Natural gas, a clear odorless gas, is found underground, often near or associated with crude oil reserves. Exploration and extraction of natural gas is part of the oil and gas extraction industry, covered elsewhere in the Career Guide to Industries. Once found and brought to the surface, it is transported throughout the United States, Canada, and Mexico by gas transmission companies using pressurized pipelines. Local distribution companies take natural gas from the pipeline, depressurize it, add its odor, and operate the system that delivers the gas from transmission pipelines to industrial, residential, and commercial customers. Industrial customers, such as chemical and paper manufacturing firms, account for more than a third of natural gas consumption. Residential customers who use gas for heating and cooking, electric utilities, and commercial businesses—such as hospitals and restaurants—account for most of the remaining consumption.

Water, sewage, and other systems. Water utilities provide about 100 gallons of fresh, treated water every day for each person in this country, or close to 40 billion gallons per day nationwide. Water is collected from various sources such as rivers, lakes, and wells. After collection, water is filtered, treated, and sold for residential, industrial, agricultural, commercial, and public use. Depending on the population served by the water system, the utility may be a small plant in a rural area that requires the occasional monitoring of a single operator or a huge system of reservoirs, dams, pipelines, and treatment plants, requiring the coordinated efforts of hundreds of people. Sewage treatment facilities operate sewer systems or plants that collect, treat, and dispose of waste from homes and industries. Other utilities include steam and air-conditioning supply utilities, which produce and sell steam, heated air, and cooled air.