Replace your incandescent light bulbs with compact fluorescent lights (CFLs)
Look closely at labels when buying light bulbs. Those marked as CFLs last 10 times longer and use 66 percent less energy than incandescent bulbs while delivering the same light levels. As a result, CFLs accrue net savings between $30 and $45 over their lifetimes, depending on your cost of electricity, the wattage size of the CFL, and the lamp's lifespan (manufacturers make CFLs that last 6,000, 8,000, or 10,000 hours).
The return on investment is 15 times higher than leaving your money in a bank account or the average return on Dows-Jones stock investments. CFLs also reduce the release of greenhouse gas emissions and are safer because they burn at a lower temperature (160° F or less) than incandescent and halogen lights, which can burn at temperatures up to 500° F. To learn more download this PDF from energystar.gov.