Solar Energy

The sun has produced energy for billions of years. Solar energy is the sun's rays (solar radiation) that reach the earth.

Solar energy can be converted into other forms of energy, such as heat and electricity. In the 1830s, the British astronomer John Herschel used a solar thermal collector box (a device that absorbs sunlight to collect heat) to cook food during an expedition to Africa. Today, people use the sun's energy for lots of things.

Solar energy can be converted to thermal (or heat) energy and used to:

  • Heat water - For use in homes, buildings or swimming pools
  • Heat spaces - Inside greenhouses, homes and other buildings


PV devices or "solar cells" change sunlight directly to electricity. PV systems are often used in remote locations that are not connected to the electric grid. They are also used to power watches, calculators, and lighted road signs.

Solar Power Plants

Indirectly generate electricity when the heat from solar thermal collectors is used to heat a fluid which produces steam that is used to power generators. Out of the 15 known solar electric generating units operating in the United States at the end of 2006, 10 of these are in California and 5 in Arizona. No statistics are being collected on solar plants that produce less than 1 megawatt of electricity, so there may be smaller solar plants in a number of other states.

The major disadvantages of solar energy are:

  • The amount of sunlight that arrives at the earth's surface is not constant. It depends on location, time of day, time of year, and weather conditions.
  • Because the sun doesn't deliver that much energy to any one place at any one time, a large surface area is required to collect the energy at a useful rate.

Ways to Use Solar Energy in Your Home

Water Heater

Water heating accounts for a large chunk of the green house gas produced by an average household's energy use and 15 percent of a home's energy bills. Every 3.5 gallons of water heated by a conventional electric water heater generates more than two pounds of emissions. There are more efficient ways to heat your household water, including on-demand, tank-less, and heat-pump water heaters.

Solar Panels

As the technology improves and production costs come down, solar panels are becoming more viable for the average household. Though it is initially expensive to set up, a photovoltaic system will generate power for thirty years and pay for itself in about eight. And every kilowatt-hour of electricity you avoid using will keep more than 1.5 pounds CO2 emissions from polluting the air. To find out if you are eligible for tax credits on solar panels and other energy-efficient home improvements visit the Database of Energy Efficiency website.