Comparing Major Sources of Electricity Generation

Instructor: Amanda Robb
In this lesson we'll review the basic process for generating electricity, go over the four main types of electricity generation in the United States such as coal, natural gas, nuclear and hydroelectric power, and then touch on other, renewable sources.

How Is Electricity Generated?

Right now, you're using electricity. It's charging your computer and keeping your food refrigerated. You probably know the electricity is generated at a power plant, but how do you make electricity? Inside power plants, massive coils of wires attached to a turbine rotate through a magnet. The magnet creates electricity in the wires through electromagnetic induction. The electricity is then transferred to your home. Different energy sources power the turbines and is the topic of our lesson today.

Electromagnetic induction
electromagnetic induction


Coal is a fossil fuel which come from years of compression of organic matter inside the Earth. Although coal is a convenient energy source, coal mining can be dangerous to workers and damage the environment. Burning coal also releases hazardous chemicals, including high levels of carbon dioxide which causes global warming.

An aerial view of the chemical spill from a coal plant in Tennessee in 2008
coal spill

Although widely used, coal is one of the more expensive forms of energy, costing 6.4 cents per kilowatt-hour. That's enough power to keep your fridge on for about 10 hours. However, the cost to the environment is the highest of all fossil fuels. Over two pounds of carbon dioxide is produced for every kilowatt-hour. Although two pounds might not seem like a lot, two pounds of carbon dioxide is enough to inflate an exercise ball to five feet across!

Natural Gas

Natural gas is also a fossil fuel and is obtained through drilling oil wells. Like coal mining, natural gas processing uses many chemicals which contaminate both air, ground, and water sources. In addition, the drilling sites and pipelines can disrupt ecosystems and local communities.

Pipeline construction for a natural gas line
pipeline construction

Natural gas produces about half the amount of carbon dioxide compared to coal, only 1.12 pounds per kilo-watt hour, and can be produced at a lower cost of only 1.4 cents. However, even though natural gas is cheaper, the up front costs to build a plant are higher than coal, and many coal plants already exist.

Nuclear Power

Nuclear power uses radioactive materials like uranium and plutonium to generate electricity. Although nuclear power only emits 0.026 pounds of carbon dioxide per kilowatt-hour, roughly 75 times less than coal, there are some serious environmental concerns and a greater cost of seven cents per kilowatt-hour.

Nuclear power plant in Georgia
nuclear power plant

When you think of nuclear power, you might think of oozing barrels of toxic, green slime. However, although toxic waste is produced, there are strict regulations. Some waste is recycled into new fuel, used in science or medicine. Other waste must be contained and diluted according to the level of radioactivity. However, radioactive waste becomes less toxic as time goes on, through a process called radioactive decay.

Nuclear waste storage in Nevada
nuclear waste

Safety is paramount at a nuclear power plant. In 1986 the nuclear power plant in Chernobyl melted down, producing radiation that killed people instantly and spreading radioactive material far into Europe. Wildlife, humans and animals died and future generations suffered from genetic diseases induced by the radiation.


Costing about seven cents per kilowatt-hour, hydroelectric power uses water stored behind a dam, creating a reservoir of water elevated above the power plant. The water is allowed to flow through the dam, creating the mechanical force needed to turn the coils of wire used to make electricity. But what happens when the reservoir runs out? Well, the reservoir is actually refilled naturally through our planet's water cycle. The heat from the sun evaporates water into the clouds, which then returns to the Earth as precipitation, refilling the reservoir.

The Hoover Dam provides electricity all through Nevada
Hoover Dam

Although hydroelectric plants release low levels of carbon dioxide, only 0.5 pounds per kilowatt-hour, they pose other environmental risks. Damming local water sources or diverting water from streams can damage local ecosystems. In addition, the stagnant pool of water causes many plants to die. When the plants die, they decompose and produce another toxic gas called methane as well as a small amount of carbon dioxide. Methane also causes global warming.

Comparing energy sources
comparing energy sources

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