Energy Sources

Power plants rely on primary “fuels” to create electricity to supply to the power grid. The main sources used to generate electricity in the United States are:

Fossil Fuels

Coal, petroleum (oil), and natural gas are examples of fossil fuels. Found in the earth, these resources were formed thousands of years ago from the remains of living organisms. Supplies of them are large but not endless. Together, fossil fuels generate about 60 percent of the electricity in the United States.

Fossil fuels are burned, which releases stored chemical energy. But the process also releases emissions of sulfur dioxide and nitrogen oxide. These pollutants are known to cause 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 increased greenhouse gasses and global climate change. Modern environmental laws are trying to limit these pollutants.

Natural gas has become the fuel of choice for new power plants. It creates fewer emissions than coal or oil. A natural gas plant can come on-line quickly during periods of maximum, or peak, demand. It also is faster and cheaper to build when compared to constructing a large coal-fired plant that runs constantly to meet an area’s base load demand.

Nuclear Power

Nuclear power involves controlled nuclear fission, or atom-splitting. The reaction releases heat energy to power boilers to spin turbines to create power. Nuclear power generates about 20 percent of the United States’ electric power. Nuclear power plants have almost no harmful emissions. But radioactive waste remains hazardous for a long time. Its disposal presents concerns. Operating nuclear power plants safely also is an important issue.

Renewable Energy

Renewable energy comes from resources that are sustainable — they naturally replenish themselves. They avoid most emissions issues linked to fossil fuels. They often supplement other fuels to meet peak customer demand. Together, they generate about 20 percent of the United States’ electricity.

Wind power uses the kinetic energy from moving air. It is clean and cost-effective. But it relies on large and noise-generating wind turbines. And it requires wind to generate power. About 8.5 percent of the nation’s electric power comes from wind. 

Biomass power is generated through burning plant or animal material, such as wood. It does not require a public utility company to provide electricity. But it can be inefficiently produced. And burning biomass creates both emissions and smoke that are harmful to the people who rely on it. It produces about 1.5 percent of the nation’s electric power.

Solar power uses photovoltaic cells instead of turbines to convert sunlight into electricity. But sunlight is necessary to generate power. And both the manufacture and the installation of solar panels can be expensive. Solar power generates a little more than 2 percent of the United States’ electric power.

Hydroelectric power relies on the kinetic energy from moving water. It is comparatively cheap and its supply likely won’t run out. But building plants requires careful study to protect natural habitats. Hydroelectric power generates about 7 percent of the United States’ electricity.

Geothermal power harnesses heat energy from the earth. It is a constant energy source, unlike solar or wind power. Yet when it is extracted from the ground, it releases some greenhouse gasses (but far less than fossil fuels). A geothermal system also requires a section of land next to the structure to which it will be providing energy. That is not practical for city dwellers. Geothermal power produces less than 1 percent of the nation’s electricity.