Light emitting diodes (or LEDs) are most definitely an upgrade from traditional fluorescent or metal halide lights. Making the switch to LED lighting can save you a hefty amount of money in the long run. But what about lumen depreciation? If this is a foreign term to you, read on to find out more about lumen depreciation and better understand your LED lighting.

What is lumen depreciation?

Even though it is well known that LED lights have a significantly longer lifespan than fluorescent or metal halide lights, it's also fact that no light bulb lasts forever. Unlike traditional lights, LEDs don't just suddenly fail and leave you in darkness. Instead, LEDs gradually emit fewer and fewer lumens over their lifespan. Let's break this down a little...

"Lumens" are the units used to measure the brightness of a light. Greater lumens emitted = brighter light.

When an LED light is first installed, it emits "initial lumens" - or the amount of light produced immediately after stabilizing, but before depreciation begins. This is when the LED is at its brightest and greatest output.

Over time, the quantity of light emitted from the LED decreases. This process is called "depreciation."

Lumen depreciation can be calculated at any time using a relatively simple equation. Take the LED's lumen output at any point in time ("mean lumens") and divide it by the LED's inital lumen output. The result of this equation will be a decimal. For example, a quotient of 0.8 reflects that the LED is functioning at 80% of its initial capacity.

So, at what point is an LED bulb considered "failed" or require replacement?

While there is some debate to this topic, the generally accepted time to replace LED bulbs is when they produce 70% or less of their initial lumen output. This time point is called the "lumen maintenance lifetime," also dubbed L70. The lifespan of an LED light is measured in hours. L7o is equivalent to the number of hours of light provided by an LED before reaching 70% of initial output.

Take a look at the LumeGen 2'x4' flat panel LED shown below. Note the yellow box reflecting this product's L70. This flat panel will provide you with 50,000 hours of excellent lighting before reaching 70% of initial output!

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