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Lumen Depreciation: Explained Simply

When we talk about replacing a customers lighting, we always try to alleviate the current costs that old and inefficient lighting fixtures incur while keeping (if not improving) our current quality of light in place.

This is done with the obvious options such as:
  • Switching away from less efficient to more efficient lighting technology (e.g switching from Metal Halide to LED)
  • Buying DLC listed lighting fixtures
  • Using a dimmer on dimmer compatible lights

Although with any lighting technology, whether that be Metal Halide, HPS, Florescent, or LED, they all suffer from something we call lumen depreciation.

Lumen depreciation is the process in which the total output of lumens a fixture produces decreases during its lifetime. The rate at which a fixtures lumens depreciate can depend on a multitude of factors which include (but are not limited to): the type of lighting technology used, total hours used, and various other factors.

Did you know that florescent and LED lamps are typically the lowest to depreciate it's lumens, while technology like Metal Halide and HPS are typically the fastest to depreciate it's lumen output? 

While LED is the the winner overall in lumen depreciation by design, fluorescent lights aren't too far behind and not nearly as bad as Metal Halide or HPS lights. Here at MyLEDLightingGuide, we would recommend you get LED for a lot more reasons then just slower lumen depreciation.
As any good facility manager, business owner, or whomever is in control of lighting within a building; planning for lumen depreciation and other light loss factors between your maintenance schedules in your lighting scheme is crucial to proper luminance throughout the lighting fixtures lifetime.

Maintenance Factor of LEDs

Something known as the maintenance factor, is an estimate on how much the initial lux level is reduced within a lighting scheme. This is a very important to calculate as it will tell us how much light their will be in a space a few years down the line. This allows us to appropriately plan and install the proper and correct amount of lamp fixtures into our building in the present.
A typical result of trying to offset lumen depreciation, a lot of installations are over lit to offset this calculation which leads to obvious increases in capital costs and not-so-needed extra energy consumption from the extra fixtures being used.
When maintenance schedules are not adhered to, although seems like an easy option to do in the moment, can lead to some nasty legal issues down the road. Without maintenance schedules, lumen output can drop to such levels that installations no longer comply with the required lux levels as listed in HSG38 and CIBSE. As a result; if any accidents were to happen, liabilities can open up due to less-than-required lux levels in your space.
Too offset these types of issues, light fixtures that can offer "constant lumen output" are optimal for ensuring lumen output levels are consistent throughout a fixtures life. This is done by increasing the output of the driver as lumen depreciation kicks in. While things like dirt accumulation (measured by Luminaire Dirt Depreciation) are still issues that need to be addressed even with such a fixture, this provides a less maintenance way to deal with the issue of lumen depreciation.

On top of that, by implementing this type of technology over simply installing more lights up-front, you can highly reduce costs on both fixtures and energy consumption which can add up quickly while dealing with lumen depreciation.

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