How to Determine Lamp Lumen Depreciation

a guest post by Brad Picht, Manager, Lighting Business Development at Graybar

How to Determine Lamp Lumen Depreciation

Lamp lumen depreciation is a factor used by lighting designers to predict the depreciation in light output for a specific light source over a defined period of time. Defining the specific lamp lumen depreciation depends on the type of light source, such as metal halide, fluorescent or LED. Also a factor is the rated life the light source is being measured at. Not all LED systems are created equal. Some LED fixtures are rated to 25K hours at L70 and others up to +100K hours at L70. Lamp lumen depreciation will be different based on the hours of operation being considered. One system may be at the end of life at 25K, while the other may have only depreciated 2 to 3 percent for the same timeline. HID, fluorescent and LED light sources all depreciate at different rates.

For example, 400W metal halides can depreciate 25 to 30 percent in light output over 8,000-10,000 hours, while typical fluorescents can depreciate between 5 to 10 percent over the same 8,000-10,000 hours. At the same time, most LEDs will depreciate 30 percent between 50,000-100,000 hours.

Lamp Lumen Depreciation and LEDs

Lumen depreciation is just one of the many reasons why LED light sources have an advantage over more traditional light sources. Not only do LEDs have a longer lifespan, but the amount of comparable depreciation for LEDs is over a longer timeframe, allowing designers to use fewer fixtures because they do not have to over design lighting systems. Lamp lumen depreciation also takes into account the inevitable percentage of lamp failures – burnt out light bulbs – or ballast failures that riddle an older space. Some manufacturers are able to adjust the current to the LED diodes to compensate for lumen depreciation to maintain an even light level over the life of the fixture. Please keep in mind not all manufacturers use this technology, but if it’s available it can reduce energy cost by 15-20 percent and it can help extend the usable life of the LED light fixture.

Working to Your Advantage

Interested in learning more about lamp lumen depreciation? Graybar has lighting specialists nationwide who can help you design and select the correct product for your application. Our lighting specialists can help with areas such as maintenance, energy, quality of light, proper light levels, lighting controls and more.

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Brad Picht Brad Picht is a NCQLP Lighting Certified Professional with over 20 years of experience in the lighting industry. Picht has been a key member of Graybar’s Lighting Business Development team for the past two years, helping to assist customers with designing and selecting the correct lighting products for each specific application.