This simple calculator assumes that incandescent bulbs are the most common 60-watt bulbs, and that CFLs provide 75 percent savings and LEDs provide 80 percent savings, based on the performance of the models on the market in 2011. Relying on the latest U.S. government and state of California studies, it assumes the typical household lamp is used 1.9 hours per day. The calculator uses the U.S. government's estimate that the average household has 40 light bulbs. Based on the U.S. market profile for 2010, the calculator assumes 16 percent of light bulbs, or an average 6.4 per household, are CFLs.

Calculations are based on 2010 U.S. Census data showing 113.7 million households in the United States.

Figures on carbon emissions are based on the U.S. Environmental Protection Agency's assumption of 1.37 pounds of carbon dioxide equivalent (CO2e) for every household kilowatt-hour of energy consumed. The calculator also uses EPA's green power equivalency assumptions, of 5.1 metric tons of CO2e for every car, 183.65 metric tons CO2e for every coal railcar, and 4,023,304 metric tons CO2e annually for every power plant.

Cost calculations are based on the average residential price of electricity in the United States in 2011, 11.6 cents per kilowatt-hour.

Credits: Programming by Stefan Estrada. Illustrations by H2H Graphics & Design. Text by Marianne Lavelle. Production by Christina Nunez.


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