What Makes the Generators Run?

Electric generating plants use different forms of energy to run pressurized steam boilers and drive their turbines. The main sources of energy are:

Fossil Fuels
Burning releases stored chemical energy from coal, oil, or natural gas. Supplies of these mineral resources are large, but not endless.

Burning releases emissions of sulfur dioxide and nitrogen oxide. Environmental laws limit these pollutants because of potential health problems, acid rain issues, and other concerns. Burning fossil fuels also releases carbon dioxide into the atmosphere. The Intergovernmental Panel on Climate Control (IPCC) has linked carbon dioxide emissions from human activities to global climate change.

The Edison Electric Institute says that natural gas is now the fuel of choice for new power plants. “Natural gas creates far fewer emissions than would be created by the combustion of coal or oil,” notes spokesperson Jim Owen. Until recently, natural gas was also fairly cheap, compared to other fuels.

“Natural gas is an ideal peaking fuel,” adds Owen. In other words, a natural gas plant can come on-line quickly during periods of maximum, or peak, demand. It's also faster to build such a plant, versus constructing a large coal-fired plant that runs constantly to meet an area's base load demand.

Hydroelectric Power
Kinetic energy from moving water is a renewable resource. The supply won't run out within a foreseeable time period. Water power is comparatively cheap. Plus, it avoids most emissions issues linked to fossil fuels. Building plants requires careful study to protect natural habitats.
Nuclear Power
Controlled nuclear fission, or atom-splitting, releases energy to power boilers. Nuclear plants have almost no emissions. But disposal of used radioactive waste presents concerns. Operating safety is also an important issue.
Solar power uses photovoltaic cells to convert sunlight into electricity. Wind power uses the kinetic energy from moving air. Geothermal power harnesses heat energy from the Earth.

Presently, utilities use these renewable energy sources mostly to supplement other fuels to meet peak customer demand.

How is your electricity generated? It depends on where you live. In the Middle Atlantic states, coal and nuclear power each produce just over one-third of the area's electricity. In some midwestern, mountain, and southern states, coal accounts for over two-thirds of the electricity generated. Hydroelectric power generates over 40 percent of the electricity for some areas along the Pacific coast.


  • combustion: The process of burning.
  • emission: A substance discharged into the air, especially by an internal combustion engine.
  • kinetic energy: energy from a moving object
  • radioactive: Of, caused by, or having the process or property by which certain chemical elements, such as radium, give off energy in the form of rays.
  • renewable resource: A resource, such as wind, that is easily replaced.

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  1. What kind of power plant does your electric company use to deliver electricity to your home? Does the electric company use one kind of power, or does it use more than one?
    [anno: Answers will vary.]
  2. What are some of the energy conservation tips that your electric company provides to its customers? Make a list of the energy conservation tips that your electric company provides that you follow at home.
    [anno: Answers will vary but should include a list of tips that the student follows at home, such as turning off lights that are not being used.]
  3. An electric company makes money by selling electricity. Why do you think that the electric company encourages people to use less energy? Write a sentence or two explaining your answer.
    [anno: Answers will vary but may include that the electric company might encourage conservation because it is good for the environment and it is good for the electric company in the long run. If we run out of resources on the planet, the electric company will not have anything to sell in the future.]