The Truth about LED Lifetimes
August 11, 2015
When evaluating the real lifetime of an LED (Light-Emitting Diode) light, it is important to understand the various factors that impact the life of the LED in comparison to other light sources. Incandescent lamps and compact florescent lamps (CFLs) can be tested through established procedures through the Illuminating Engineering Society of North America (IESNA). However, since LED lifetimes are so lengthy, IESNA must use a different procedure to determine the length of an LED light as testing for 50,000 hours continuously would take an unrealistic amount of time (5.7 years).
All electric lights experience lumen depreciation, which is a gradual decrease in the light that is emitted through the bulb over time. Incandescent lamps experience 10-15% depreciation over a 1,000 hour life. In comparison, CFLs lose up to 20% of their initial lumens over a 10,000 hour life. As lumen depreciation accelerates, lamps gradually reduce their ability to produce light. The question for LED lamps then becomes: at what point does this decrease reach such a level that there is an unacceptable level of light being emitted? This would signal the end of the useful life of the LED.
According to the U.S. Department of Energy, the Alliance for Solid State Illumination Systems and Technologies (ASSIST) recommends that useful life should be defined as the point in which the light output has declined to 70% of its initial lumens (L70) for general lighting and 50% of original lumens (L50) for decorative purposes.
The U.S. Department of Energy provides the following table to rank various light sources by their useful life:
|
Range of Typical Rated Life (Hours) |
Estimated Useful Life (L70) |
| Incandescent |
750-2,000 |
|
| Halogen Incandescent |
3,000-4,000 |
|
| Compact fluorescent (CFLs) |
8,000-10,000 |
|
| Metal halide |
7,500-20,000 |
|
| Linear fluorescent |
20,000-30,000 |
|
| High-Power White LED |
|
35,000-50,000 |
An interesting aspect regarding the 35,000-50,000 hour estimate is that some manufacturers claim that the useful life (L70) can actually be doubled to 100,000 hours, depending on drive current and operating temperature through intelligent lighting controls. That means that LEDs could last for 11 years if running continuously!
The cost savings quickly become quite apparent when one analyzes the graph above and considers the positive return on investment that LED lights produce when compared to other standard light sources. This can have huge long-term savings potential for businesses which has become apparent to many companies as LED installation continues to grow into its very promising future.