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Learn About LEDs

What are LEDs?

LED stands for light-emitting diode. LEDs are small light sources that become illuminated by the movement of electrons through a semiconductor material. LEDs can be integrated into all sorts of products to provide white and colored light, such as flashlights, light bulbs, and integrated light fixtures.

Low-Powered LEDs

LEDs used to draw attention to something, such as an exit sign,
a green power button on a computer, or a red blinking
light on a video camera.

High-Powered LEDs

LEDs used to illuminate an area. ENERGY STAR qualified LED lighting uses multiple illuminator LEDs inside a fixture to produce white light.
Indicator LED illustration illuminator LED illustration

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What is Solid-State Lighting?

LED desk lamp with many LEDs

Many tiny LEDs are used in
each fixture.

LEDs are part of a family of lighting technologies called Solid-State lighting. This family also includes OLEDs (Organic Light Emitting Diodes). OLEDs (pronounced OH-leds) consist of sheets of carbon-based compounds that glow when a current is applied through transparent electrodes. While not yet market ready, OLEDs will function like a thin film on a wall or ceiling that illuminates a room. Like LEDs, OLED technology is advancing rapidly.

Solid-State lighting (SSL), most commonly seen in the form of Light Emitting Diodes (LEDs), has the potential to revolutionize the efficiency, appearance, and quality of lighting as we know it.

The U.S. Department of Energy estimates that rapid adoption of LED lighting in the U.S. by 2027 could;

  • Deliver savings of about $265 billion.
  • Avoid 40 new power plants.
  • Reduce lighting electricity demand by 33% in 2027.
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How are LED lighting products different from other lighting, like fluorescent or incandescent?

LEDs emit light in a specific direction, whereas an incandescent or fluorescent bulb emits light — and heat — in all directions. For direct lighting applications LED lighting uses both light and energy more efficiently.

For example, an incandescent or compact fluorescent (CFL) bulb inside of a recessed can will waste about half of the light that it produces, while a recessed down light with LEDs only produces light where it’s needed — in the room below.

Incandescent bulbs create light by passing electricity through a metal filament until it becomes so hot that it glows. Incandescent bulbs release 90% of their energy as heat.

In a CFL, an electric current is driven through a tube containing gases. This reaction produces ultraviolet light that gets transformed into visible light by the fluorescent coating (called phosphor) on the inside of the tube.

LED lighting products use light emitting diodes to produce light very efficiently. The movement of electrons through a semiconductor material illuminates the tiny light sources we call LEDs. A small amount of heat is released backwards, into a heat sink, in a well-designed product; LEDs are basically cool to the touch.


LED lighting, when designed well, can be more efficient, durable, versatile and longer lasting than incandescent and fluorescents lighting.


LED lighting, when designed well, can be more efficient, durable, versatile and longer lasting than incandescent and fluorescents lighting.

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Basic parts of LED lighting

LED lighting starts with a tiny chip (most commonly about one square millimeter) comprised of layers of semi-conducting material. LED packages may contain just one chip or multiple chips, mounted on heat-conducting material called a heat sink and usually enclosed in a lens. The resulting device, typically around 7 to 9 mm on a side, can be used separately or in arrays. LED devices are mounted on a circuit board, which can be programmed to include lighting controls such as dimming, light sensing and pre-set timing. The circuit board is mounted on another heat sink to manage the heat from all the LEDs in the array. The system is then encased in a lighting fixture, architectural structure, or even a “light bulb” package.

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Aren’t all LED lights highly efficient and long-lasting?

LED with normal color after 100 hours
LED discolored after 1000 hours

After less than a year of use, a poorly designed LED product can flicker, shift in color, look dim, offer uneven light, or continue to use power when turned off, among other problems.

Not necessarily. LEDs have been efficient and long lasting as indicator lights in electronics for years, but using LEDs to create stable white light for general lighting presents new challenges. The key to success is smart design. To qualify for ENERGY STAR, LED lighting products must pass a variety of tests to prove that the products will display the following characteristics:

  • Brightness is equal to or greater than existing lighting technologies (incandescent or fluorescent) and light is well distributed over the area lighted by the fixture.
  • Light output remains constant over time, only decreasing towards the end of the rated lifetime (at least 25,000 hours or 22 years based on use of 3 hours per day).
  • Excellent color quality. The shade of white light appears clear and consistent over time.
  • Efficiency is as good as or better than fluorescent lighting.
  • Light comes on instantly when turned on.
  • No flicker when dimmed.
  • No off-state power draw. The fixture does not use power when it is turned off, with the exception of external controls, whose power should not exceed 0.5 watts in the off state.

Bad design can lead to a wide range of problems, some immediately observable and some not. Poorly designed products often come with exaggerated claims while failing to deliver on the quality specifications above.

Choose ENERGY STAR quailified LED fixtures to ensure the products you purchase perform well.

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