FMO: WHY LUMEN DEPRECIATION IS TOO IMPORTANT FOR YOU.

 

CFMO: 
WHY LUMEN DEPRECIATION IS TOO IMPORTANT FOR YOU.

 

LEDs, like all light sources, lose light over time. It’s important to define lighting goals and objectives for your design and also be aware of common mistakes in applying lumen depreciation data to LED fixtures.

LEDs, like all light sources, lose light over time. The term used to describe this is sometimes referred to as lumen depreciation. In lighting design, understanding the rate of this decline over time can help determine the amount of light available at some point in the future. For a little historical perspective, the rate at which legacy HID lamps lost light over time occurred much faster compared to LEDs. In addition, the rate of decline for HID lamps was not influenced by product design, therefore rules were put in place and applied equally across all manufacturers products as it related to lumen depreciation.

 

LED luminaires are different. First, LED luminaires are designed to lose light at a much slower rate than the legacy products they were designed to replace – eliminating costly re-lamping events. Second, not all LEDs deliver the same performance as it relates to lumen depreciation; therefore, if manufacturers are using different LEDs, you’ll likely get different results. In addition, an LED’s performance will also be influenced by product design. The amount of current a manufacturer decides to apply to the LED, as well as how the product is designed to thermally manage the temperature at the LED itself, will also influence light loss over time. Lastly, it should be noted that lumen depreciation data is not a statement on product life. Many misinterpret statements like L₇₀ to reflect product life, but it does not. L₇₀ statements simply predict when the LED will be at 70% of its initial light output or 30% lumen depreciation, under the conditions for that product. It makes absolutely no claims on the expected “life” of the overall luminaire.

 

When it comes to properly applying lumen depreciation data to LED luminaires, there are some common mistakes. These include ignoring that lumen depreciation occurs and/or assuming that it occurs at the same rate across all products. In addition, many fail to consider and define the useful or expected application life of their design. Since lumen depreciation occurs over time, defining a useful or expected application life is critical to selecting a corresponding lumen depreciation value based on your defined application life. Lastly, it’s critical to define your lighting goals and objectives, helping ensure that when your lumen depreciation value is applied to your design, you are confident that your lighting system will continue to produce enough light to meet the illumination requirements of your application over its entire designed life.