Average Rated Life - What Does it Mean for Light Bulbs?

Lighting Basics

In the light bulb industry, ARL, or average rated life, is the standard measure of how long half a batch of light bulbs can last before they fail. ARL is also known by the more common term, half-life. The ARL of a light bulb is determined by rigorous testing. For example, if a batch of 1000 light bulbs have an ARL of 5000 hours, this means that no more than 50% or 500 of the light bulbs tested failed upon reaching 5000 hours of testing. Although some may have failed within 2500 hours or 3000 hours, what is important is that half of the batch succeeded in reaching the 5000-hour threshold.

The mere action of turning a light bulb on or off can affect the ARL directly. However, LED bulbs, incandescent, and halogen bulbs aren't affected as much as fluorescent bulbs are. In a nutshell, a bulb that only gets turned off or on once a day lasts longer than a bulb who gets turned off or on several times per day.

However, when ARL tests are conducted, testing conditions allow bulbs to perform optimally. Should the bulb be placed somewhere where it is too hot, too wet, too cold or with too much vibration, the ARL output of the bulb can be significantly reduced even further, thereby reducing its lifetime.

Here’s a quick look at the Average Rated Life of different light bulb types

  • Incandescent Bulbs - 500 to 2000 hours
  • HID Lamps - 25,000 hours
  • CFLs - 15,000 hours
  • Halogens - 3000 hours
  • LED Bulbs - 50,000 hours

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