The Efficiency of Light Bulbs

Strictly speaking, light bulb efficiency is measured in lumens per watt, or the amount of light emitted divided by the amount of energy used to produce the light. Additional considerations include the bulb's lifetime and the amount of heat it produces.

Lumens per Watt

• Incandescent light bulbs produce the least amount of lumens per watt. light bulb image by Photosani from Fotolia.com

  Using lumens per watt, incandescent and halogen lights are the least efficient. Incandescent lights average only 10 to 17 lumens per watt. Halogen lights provide 12 to 15 lumens per watt. Compact fluorescent light bulbs emit 40 to 70 lumens per watt, and high-pressure sodium produces 50 to 140.

Compact Fluorescent Light Bulbs

• CFLs last longer, burn cooler, and use less energy than incandescent bulbs. Compact fluorescent lightbulb image by K. Geijer from Fotolia.com

  The U.S. government Energy Star program considers compact fluorescent bulbs, or CFLs, among the most efficient. They last ten times longer than incandescent bulbs, and use 75 percent less energy. They generate less heat, which results in lower cooling bills. Because of the lower temperature, they are safer, with less likelihood of fires and burns.

Light-Emitting Diode

• LED lights do not require time to warm up. Led headlight image by Aleksandr Ugorenkov from Fotolia.com

  Light-emitting diodes, or LEDs, produce fewer lumens per watt than CFLs, but more than incandescent lights. The government's Energy Star program lists them as using 75 percent less energy than incandescent lights. They last 15 times longer and burn cooler than incandescent bulbs. While CFL bulbs require a warm-up time, LEDs do not.