In 2008, the United States used approximately 99.2 quads. One quad is about as much total energy as the city of Chicago requires in one year.

In 2008, the United States used approximately 99.2 quads. One quad is about as much total energy as the city of Chicago requires in one year.

All of the reasons mentioned are considered obstacles to producing cars that run on hydrogen fuel cells.

All of the reasons mentioned are considered obstacles to producing cars that run on hydrogen fuel cells.

All of the reasons mentioned are considered obstacles to producing cars that run on hydrogen fuel cells.

Nuclear power accounted for 9% of the U.S. energy supply in 2008.

Nuclear power accounted for 9% of the U.S. energy supply in 2008.

In 2008, industry used 31% of the total energy used; next was transportation at 28%, then residential at 22%, and commercial at 19%.

In 2008, industry used 31% of the total energy used; next was transportation at 28%, then residential at 22%, and commercial at 19%.

In 2008, industry used 31% of the total energy used; next was transportation at 28%, then residential at 22%, and commercial at 19%.

The average U.S. car gets 21.4 mpg. About 19 pounds of carbon dioxide are emitted for every gallon burned, or 0.9 lb/mile.

The average U.S. car gets 21.4 mpg. About 19 pounds of carbon dioxide are emitted for every gallon burned, or 0.9 lb/mile.

Mining coal disturbs the land and modifies the chemistry of rainwater runoff, which in turn affects stream and river water quality.

Lighting accounts for 18% of the electricity used in the United States. A 12% decrease in overall electricity use in buildings could be realized if incandescent bulbs were replaced with CFL or LED bulbs.

Roughly 21% of the electricity used in residential and commercial buildings goes to lighting.

Roughly 21% of the electricity used in residential and commercial buildings goes to lighting.

Roughly 21% of the electricity used in residential and commercial buildings goes to lighting.

Consuming the largest amount of energy, space heating accounts for 31% of all residential energy used. Space cooling accounts for an additional 12% of energy usage.

Consuming the largest amount of energy, space heating accounts for 31% of all residential energy used. Space cooling accounts for an additional 12% of energy usage.

Consuming the largest amount of energy, space heating accounts for 31% of all residential energy used. Space cooling accounts for an additional 12% of energy usage.