Light Switch Calculator

Compact fluorescent light bulbs (CFLs) are a great way to save energy in your home. They cost more to buy but quickly return that money through lower monthly utility bills. Use this calculator to see how much your family might save by replacing standard 100-watt incandescent light bulbs with CFLs.

In addition to these savings on utility bills, CFLs last almost 10 times longer than standard incandescent lamps and give off only one-quarter of the heat.

See if you can solve these:

  • If you have five 100-watt incandescent light bulbs that burn about five hours per day at a rate of 10 cents/kWh, how much do they cost?
  • How much would it cost if your home had CFLs instead?
  • What is the difference each year between the cost to operate the standard bulb and the CFL?
  • How many 50-cent candy bars could you buy with the savings over a year?
  • If the CFL costs $3, how many months would it take to save enough to buy one?
  • How many CFLs could you buy with your yearly savings?