What is LEDs durability?

LED durability, as well as the durability of other light sources, is calculated in hours as the time of lamp lighting (under particular conditions) in which it preserves the suitable usage properties. In case of LEDs, similarly as with fluorescent or other discharge lamps, which do not expire suddenly as classic bulbs, the basic criterion for determining the durability is the time during which the suitable value of luminous flux is maintained. “The suitable value” is usually defined in % of the initial value. For fluorescent and other discharge lamps, the value of luminous flux is accepted on the level from 70% to 90%. The durability of LED is similarly determined. Predominatigly, the durability of LED is defined as the lighting time during which the luminous flux will not decrease below 70% of the initial value. Such durability is indicated with L70 symbol. L50 symbol can be also found that is related to the durability for the period during which the luminous flux will not decrease below 50% of the initial value. The ruthless value of the durability declared in the second case will be higher, that still does not mean, that the product is better, however, more gentle criterions are adopted to this kind of product. The optimal solution for the user (designer) would be the presentation by the manufacturer of the values of preservation of luminous flux as a function of lighting time.

The above solutions on the topic of defined durability through the coefficient of luminous flux preservation, is only the part of characteristics of light source, including LED, indicating its durability. This feature relates to the particular product. From the user’s point of view, the declared durability of individual light source is not the only important parameter, but also an information about what percentage of the light sources reaches the declared durability L, either what percentage of the ligh sources can be damaged before the time L. In this assessment, those lamps with the highest decrease of luminous flux than it was declared, may be classified as damaged ones. Such a way of considering the durability may be defined according to the coefficient of durability (used mainly for fluorescent and other discharge lamps), indicating the percentage of lamps, which after time L still preserve its characteristics or through the coefficient of damages (mainly used for LED) indicating the percentage of LED lamps being damaged during the particular exploitation time, for instance, declared durability L. Such coefficient of damages may be defined by Fy symbol where y can be accounted as 10 or 50, and should be read as 10% or 50% of possible LED damages during the declared durability time Lx.

Comparing the durability of LEDs with different construction or made by different manufacturers, it is worth to take into consideration criterions and conditions indicated by the manufacturers. Durability may vary for different types of LED depending on the operating conditions (humidity, temperature), current value.

Data related to the durability L70 is presented below, in division of types, which may be found in the literature and in the offers of LED manufacturers.

  • LED emitting red color light – approximately 150 thousand hours.
  • LED emitting yellow color light – approximately 125 thousand hours.
  • LED emitting orange color light – approximately 250 thousand hours.
  • LED emitting green, blue and white color light – approximately 3070 thousand hours.

These durability periods occur in case of optimal values obtained in laboratory conditions, which differ from the actual ones found in lighting equipment.