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.

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.

Worldwide consumption of energy sources is projected to rise by nearly 50% between 2006 and 2030.

Worldwide consumption of energy sources is projected to rise by nearly 50% between 2006 and 2030.

The United States and Canada are both developed countries. China and India are projected to have the greatest growth in energy consumption between 2006 and 2030.

The United States and Canada are both developed countries. China and India are projected to have the greatest growth in energy consumption between 2006 and 2030.

In 2005, a million Btu of energy from coal cost approximately $2, versus $5 for natural gas and $10 for oil. However, prices can fluctuate due to changes in the economy and new government policies.

In 2005, a million Btu of energy from coal cost approximately $2, versus $5 for natural gas and $10 for oil. However, prices can fluctuate due to changes in the economy and new government policies.

90% of the coal mined in the United States was used to generate electricity in 2006.

90% of the coal mined in the United States was used to generate electricity in 2006.

In 2008, wind accounted for 0.5% of America's energy portfolio.

In 2008, wind accounted for 0.5% of America's energy portfolio.

Electricity is a secondary energy source because it can only be produced from the use of primary energy sources such as coal, natural gas, or nuclear reactions.

Electricity is a secondary energy source because it can only be produced from the use of primary energy sources such as coal, natural gas, or nuclear reactions.

Electricity is a secondary energy source because it can only be produced from the use of primary energy sources such as coal, natural gas, or nuclear reactions.

Electricity is a secondary energy source because it can only be produced from the use of primary energy sources such as coal, natural gas, or nuclear reactions.

Tidal energy is gravitational in origin. Solar energy comes from nuclear reactions in the sun.

Tidal energy is gravitational in origin. Geothermal energy comes from radioactive decay inside the earth.

Tidal energy is gravitational in origin. Solar energy comes from nuclear reactions in the sun, and geothermal energy comes from radioactive decay inside the earth.