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About LED Lighting

What are LEDs?

LED stands for light emitting diode. LED lighting products produce light approximately 90% more efficiently than incandescent light bulbs. How do they work? An electrical current passes through a microchip, which illuminates the tiny light sources we call LEDs and the result is visible light. To prevent performance issues, the heat LEDs produce is absorbed into a heat sink.

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How is LED lighting different than other light sources, such as incandescent and CFL?

• LED lighting differs from incandescent and compact fluorescent lighting in several ways. When designed well, LED lighting can be more efficient, durable, versatile and longer lasting.
• LED lighting products use light emitting diodes to produce light very efficiently.
• Common LED colors include amber, red, green, and blue. To produce white light, different color LEDs are combined or covered with a phosphor material that converts the color of the light to a familiar “white” light used in homes.
• LEDs are now being incorporated into bulbs and fixtures for general lighting applications. Some LED light fixtures may have LEDs built in as a permanent light source.
• LEDs are directional light sources, which means they emit light in a specific direction, unlike incandescent and CFLs, which emit light – and heat – in all directions. For this reason, LED lighting can use light and energy more efficiently in many applications.
• LED bulbs that are ENERGY STAR-certified are subject to very specific requirements designed to replicate the experience you are used to with a standard A-type bulb.

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LED Basics

The useful life of LED lighting products is defined differently than that of other light sources, such as incandescent or CFL. This is because LEDs typically do not “burn out” or fail. Instead, they experience lumen depreciation, where the amount of light produced decreases and light color appearance can shift over time. Instead of basing the useful life of an LED product on the time it takes for 50 percent of a large group of lamps to burn out (as is the case with traditional sources), LED product “lifetime” is set based on a prediction of when the light output decreases 30 percent.

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LEDs and Heat

Because LED lighting systems don’t radiate heat the way an incandescent or halogen light bulb does, the heat produced from the power going into the product must be drawn away from the LEDs. This is usually done with a heat sink, which is a passive device that absorbs the heat produced and dissipates it into the surrounding environment. This keeps LEDs from overheating and burning out. Thermal management is probably the single most important factor in the successful performance of an LED product over its lifetime — the higher the temperature at which the LEDs are operated, the more quickly the light will degrade, and the shorter the useful life will be.

LED products use a variety of unique heat sink designs and configurations to manage heat, so their appearances may vary. Regardless of the heat sink design, all LED products that are ENERGY STAR-certified have been tested to ensure that they manage the heat so that the light output is properly maintained through the end of its rated life.

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• *Source — energystar.gov