High brightness white LEDs are commonly specified to last 50,000 to 60,000 hours at maximum operating conditions. When operated below these maximum conditions, they can last well in excess of 70,000 hours. Well designed fixtures that minimize the lifetime limitations of other system components can take advantage of LED longevity to deliver terrific reliability.

In order to understand the value that this lifetime delivers to lighting users, first one must understand lifetime as defined by LEDs versus traditional light fixtures. LED fixture manufacturers define fixture end of life as a 30 percent reduction in output. This is contrasted with traditional lighting like fluorescent, which typically suffers complete lamp failure. Because fluorescent lamp lifetime is defined as an MTBF, half of the lamps are dead and require replacement by the lifetime rating.

Clearly, fluorescent has the least amount of lumen degradation over time at about 5 percent, followed by high-power LED. Both of them are significantly superior to any other lamp type.

In the lifetime of the LED fixture, a fluorescent fixture will probably have required many complete relampings. This hits lighting operators particularly hard if replacing lamps impacts other aspects of their operations. Examples include lighting over operating machinery, lighting in difficult to reach or public areas.

For many companies the cost of maintaining their lighting weighs much more heavily on their P&L than does the cost of the associated energy. LEDs’ dramatic lifetime advantage can have much greater impact on these companies. What kinds of companies care more about lighting maintenance than energy? Companies that have lighting installed in difficult-to-reach places, in public areas, or both. Consider a typical convention center, where many of the light fixtures are in public areas installed in locations that are difficult to reach. Some lamps are 40 feet or even 90 feet in the air, requiring a very tall scissor lift and a two-man crew to service, making them very expensive to replace. These relampings frequently cost $150 or more per lamp.

Not only is it difficult to reach those lamps, but they typically cannot be replaced when the facility is being used, so scheduling maintenance can be very difficult. On the other hand, a convention center cannot afford to have burned-out lamps. If the facility does not look pristine, their trade show and conference business will go to another venue.