A 75-watt incandescent light bulb left on for 12 hours a day costs about $30 per year in energy. Switch to an 18-watt compact fluorescent light (CFL) that will provide the same amount of light at one-fourth the energy, and that cost drops to about $7 per year. That saves you $23 per year for just one light! And CFLs last seven to ten times longer than incandescents! LEDs (light-emitting diodes) use up to 90% less energy than incandescents and last up to 40 times longer.
The Lighting Label provides standard information for any light (click for more details).