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Guide: LED lighting terminology for trade pros


Light-emitting diodes, or LEDs, are becoming increasingly popular for commercial and residential use. LED bulbs provide superior energy savings and years of reliable performance, making them beneficial to trade professionals like commercial contractors, residential builders and facility managers.

But there are many different types of LEDs available, with varying levels of brightness, hues and power usage. Depending on its attributes, one type might be better suited for a specific application than another. This guide to LED lighting terminology will help you make sure you understand all the details to select the right bulb for your project.

LED lifespan: average rated life

When referring to the lifespan of LED bulbs, you’ll often hear the term “average rated life.” Bulbs are tested in batches to determine how long it takes for half of the bulbs to fail—that time is known as the average rated life, or ARL.

For example, if 100 bulbs are powered and 50 of them fail after 1,000 hours, then the ARL is 1,000 hours. Some of the bulbs may have failed at different times throughout the test, but the LED lifespan is measured by when half the batch failed.

LEDs last much longer than other options. The U.S. Department of Energy reports that people can expect LED lighting to perform well for 30,000 to 50,000 hours and sometimes beyond.

LED color temperature

The lighting term LED color temperature refers to a measurement that indicates the hue of a specific type of light source. Color temperature is measured by Kelvin: One unit Kelvin is equal to one degree Celsius on the Kelvin scale.

The Kelvin scale doesn’t go into the negative like Celsius does, and the higher the color temperature, the cooler the hue of light. Colors range from cool to neutral to warm.

Check out two examples of color temperature at different spots on the Kelvin scale:

  • 2700K color temperature will produce a warm white color similar to incandescent light, making it a suitable replacement for incandescent bulbs.
  • 4100K color temperature will emit a cool white light suitable for retail or work environments.

Get tips for choosing the right color and brightness of LED lighting >>

LED lumens

Brightness, or the amount of light emitted by an LED, is measured in lumens. You may see it written as “lm” to reference visible light.

The brighter the shine, the higher the number of LED lumens. A bulb that emits less light has a lower number of lumens.

LED watts

A watt is a unit of power, and the amount of energy required for a bulb to emit light is measured in watts. The higher the number of watts required to power a lamp, the more energy used.

LED lumens per watt

The number of watts required to emit a certain number of lumens is a ratio known as lumens per watt (lm/W), or luminous efficacy. This LED lighting term is particularly important to understand the energy efficiency of a particular bulb.

If a bulb can emit a higher number of lumens while using a lower number of watts, it is considered to be more energy efficient than one that requires more watts to emit the same amount of lumens.

For example, a standard 60W incandescent bulb emits 800 lumens, whereas a standard LED bulb only requires 10W to emit 800 lumens. The LED bulb is more efficient than the incandescent bulb because it can emit a higher number of lumens while using significantly less power.

Foot candle and lux

Foot candle and lux are two LED lighting terms that deal more with application than with reading a light bulb label. While lumens refers to how much light an LED emits, foot candle measures the light that actually reaches the surface or areas you want to illuminate, specifically one square foot of that surface. Lux measures that same light over one square meter instead of a foot.

Lower light is often perfect for most areas of a private residence, so choosing bulbs to create lower foot candles there would be fine. Offices or facilities like warehouses typically need more foot candles to make sure everyone can easily and safely see what they’re doing.

Ferguson can help with LED lighting terminology and more.

Our expert associates can help you find the right lighting for your needs. Or if you’re ready to apply your knowledge, shop LED lighting and brighten up your next project or building while saving energy.