The National Academies: What You Need To Know About Energy

The National Academies

What You Need To Know About Energy

Our Energy Sources

Renewable Sources

The idea of drawing our energy from sources that are renewable, are independent of foreign nations, and do not emit greenhouse gases has powerful appeal. But capturing these resources is expensive, and many are intermittent, which complicates using them on a large scale. Learn about renewable sources’ current contributions to our energy supply and their prospects for our energy future.

Renewable energy contribution to total U.S. energy consumption in 2008.


The United States generates more electricity from geothermal energy than any other country in the world.

Geothermal energy is a domestic energy source with relatively benign effects on the environment. So why does it only contribute 0.4% to the total U.S. energy supply?

More about geothermal


In the United States, the amount of electricity generated from wind in 2008 was almost five times greater than the amount generated in 2002.

Wind accounts for a very small part of our total energy production but it has been growing in the past few years. Find out how this renewable technology is contributing to our supply of electricity.

More about wind


About 0.1% of the total energy supply in the United States came from solar sources in 2008.

Sunlight is Earth’s most abundant energy source. Yet capturing and converting its energy into usable forms is a challenge. Learn how solar energy is currently being used and the obstacles we must overcome to expand its use.

More about solar


In 2008, 6% of the electricity generated in the United States came from hydroelectric sources.

Of the renewable energy sources used to generate electricity in the United States, hydropower makes the biggest contribution. Water is a cheap, domestic source of energy and it does not emit greenhouse gases. But hydropower brings with it other environmental impacts to consider.

More about hydroelectric


Biomass contributed about 4% to the total U.S. energy supply in 2008.

Of all the renewable sources, biomass contributes the most to the U.S. energy supply. Find out how methane from landfills, “grain alcohol,” and municipal waste help power our nation.

More about biomass

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Energy Hands-on

What do you know about energy?

According to the Corporate Average Fuel Economy (CAFE) standards updated in December 2007, what is the average miles per gallon (mpg) required for new cars, SUVs, and light trucks (combined) by 2020?

  • Sorry, that’s incorrect.

    Based upon the 2007 CAFE standards, the new average mpg required by 2020 is 35 mpg.

  • Correct!

    Based upon the 2007 CAFE standards, the new average mpg required by 2020 is 35 mpg.

  • Sorry, that’s incorrect.

    Based upon the 2007 CAFE standards, the new average mpg required by 2020 is 35 mpg.

Energy Defined

Global Warming

A term used to describe the phenomenon of Earth’s rising average near-surface temperature. Although such fluctuations have occurred in the past due to natural causes, the term is most often used today to refer to current warming trends. Most scientists have concluded that this is very likely due to the observed increase in human-generated greenhouse gas concentrations in the atmosphere.

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National Academies Press

Search the National Academies Press website by selecting one of these related terms.