Electricity Basics

Most of the electricity in the United States is produced using steam turbines.

A turbine converts the kinetic energy of a moving fluid (liquid or gas) to mechanical energy. In a steam turbine, steam is forced against a series of blades mounted on a shaft, thus rotating the shaft connected to the generator. The generator, in turn, converts its mechanical energy to electrical energy based on the relationship between magnetism and electricity.

In steam turbines powered by fossil fuels, such as coal, petroleum (oil), and natural gas, the fuel is burned in a furnace to heat water in a boiler to produce steam.

Fossil Fuels Generate Most U.S. Power

Coal is the most common fuel for generating electricity in the United States. In 2010, 45 percent of the country's nearly 4 trillion kilowatt hours of electricity used coal as its source of energy.

Coal Fired Power Plant

Natural gas, in addition to being burned to heat water for steam, can also be burned to produce hot combustion gases that pass directly through a turbine, spinning the turbine's blades to generate electricity. Gas turbines are commonly used when electricity utility usage is in high demand. In 2010, 24 percent of the Nation's electricity was fueled by natural gas.

Natural Gas Power Plant

Petroleum can be burned to produce hot combustion gases to turn a turbine or to make steam to turn a turbine. Residual fuel oil, a product refined from crude oil, is often the petroleum product used in electric plants that use petroleum to make steam. Petroleum was used to generate just over 1 percent of all electricity in the United States in 2010.

Nuclear Power Provides About One-Fifth of U.S. Electricity

Nuclear Power Plant

Nuclear power is a method in which steam is produced by heating water through a process called nuclear fission. In a nuclear power plant, a reactor contains a core of nuclear fuel, primarily uranium. When atoms of uranium fuel are hit by neutrons, they fission (split) releasing heat and more neutrons. Under controlled conditions, these other neutrons can strike more uranium atoms, splitting more atoms, and so on. Thereby, continuous fission can take place, creating a chain reaction releasing heat. The heat is used to turn water into steam, that, in turn, spins a turbine that generates electricity. Nuclear power was used to generate about 20 percent of all the country's electricity in 2010.

Renewable Energy Sources Make Up the Rest

Hydropower, the source for 6 percent of U.S. electricity generation in 2010, is a process in which flowing water is used to spin a turbine connected to a generator. There are two basic types of hydroelectric systems that produce electricity. In the first system, flowing water accumulates in reservoirs created by dams. The water falls through a pipe called a penstock and applies pressure against the turbine blades to drive the generator to produce electricity.

Hydroelectric Power Plant

In the second system, called run-of-river, water is diverted from a river using a relatively low dam or weir into penstocks and turbines. The dam does not store a large volume of water in a reservoir. Run-of-river power plants are more dependent on river flows than hydro plants with reservoirs for storing water which can produce electricity even when natural river flows are low.

Biomass is material derived from plants or animals (i.e. biogenic) and includes lumber and paper mill wastes; food scraps, grass, leaves, paper, and wood in municipal solid waste (garbage); and forestry and agricultural residues such as wood chips, corn cobs, and wheat straw. These materials can be burned directly in steam-electric power plants, or converted to gas that can be burned in steam generators, gas turbines, or internal combustion engine-generators. Biomass accounts for about 1 percent of the electricity generated in the United States.

Biomass Power Plant

Wind power is produced by converting wind energy into electricity. Electricity generation from wind has increased significantly in the United Statessince 1970, but wind power remains a small fraction of U.S. electricity generation, about 1 percent.

Wind Turbine

Geothermal power comes from heat energy buried beneath the surface of the earth. In some areas of the United States, enough heat rises close to the surface of the earth to heat underground water into steam, which can be tapped for use at steam-turbine plants. This energy source generated less than 1 percent of the electricity in the country in 2010.

Geothermal Power Plant

Solar power is derived from energy from the sun. There are two main types of technologies for converting solar energy to electricity: photovoltaic (PV) and solar-thermal electric. PV conversion produces electricity directly from sunlight in a photovoltaic (solar) cell. Solar-thermal electric generators concentrate solar energy to heat a fluid and produce steam to drive turbines. In 2010, less than 1 percent of the Nation's electricity was from solar power.

Solar Panels


How Electricity Gets to Your Home

Electricity Is Delivered to Consumers Through a Complex Network

Electric power is generated at power plants and then moved to substations by transmission lines — large, high-voltage power lines. In the United States, the network of nearly 160,000 miles of high voltage transmission lines is known as the "grid."

A local distribution system of smaller, lower-voltage distribution lines moves power from substations and transformers to consumers.


diagram of how electric power gets to your home



Electricity and the Environment

Although electricity is a clean and pretty safe form of energy to use, the production and transmission of electricity still impacts the environment. Nearly all types of electric power plants have some impacts or effects on the environment, some more than others.

The United States has laws to reduce these impacts. Perhaps the most important such law is the Clean Air Act, which established regulations for the control of air emissions from most power plants. The Environmental Protection Agency (EPA) administers the Act and sets emissions standards for power plants through various programs, such as the Acid Rain Program. The Act has resulted in a substantial reduction of emissions of some of the major types of air pollutants in the United States.

The Impact of Power Plants on the Landscape

All power generators or plants have a physical footprint (the area where they are placed or located). Some can be located inside, on, or next to an existing building, so the impact of their footprint is very small. Most large power plants require clearing land to locate the power plant and any necessary fuel storage areas (in the case of hydro-power dams, a reservoir forms behind the dam). Some plants may also require the construction of access roads, rail, pipelines, transmission lines, and access to cooling water supplies or reservoirs.

Besides the physical footprint, many power plants are large physical structures that have impacts on the visual landscape. Some people may not like this especially where the landscape is relatively natural or pristine.

In general, the larger the area disturbed, the greater the real and potential impacts on the landscape.

Electric Power Lines Also Have an Impact

Power transmission and distribution lines carry electricity from power plants to consumers. Most transmission lines are strung above ground on large towers. The towers and lines impact the visual landscape, especially when they pass through pristine natural areas. Trees near the wires may be disturbed and have to be managed to keep them from touching the wires and these activities can affect native plant populations and wildlife. Power lines can be placed under the ground, but this is more expensive and may result in a greater disturbance of the landscape than overhead lines.