Lumen depreciation refers to the decline of light level of a lighting source from its original output over time until it eventually goes completely dark; at that point, the light source will be considered as failed. This is a process all light sources go through, including LEDs.

As illustrated by the graph above, the amount of light a bulb emits decreases over the course of its lifetime until it eventually goes out completely. Older metal halide lights perform the worst in this regard with the fastest decline over the shortest life cycle, losing over 50% of its original brightness after half of its life. Fluorescent lights perform slightly better, but as soon as they start to reach the end of their life span you'll see a huge decrease in performance. LEDs on the other hand, experience a slight, but steady decline over a long period of time, over 50,000 hours.

To put this into perspective, imagine installing some new metal halide high bays in a warehouse. The light will be sufficient for about 5,000 hours (208 days), but your surroundings will start to get darker exponentially. By 10,000 hours your lights will be so dim you will need a flashlight to read labels let alone operate heavy machinery safely.

The same logic can apply to fluorescent lights which can be found in almost every office in the world. Less light will end up putting strain on your eyes and can result in a variety of negative effects to your physical and mental health.

Additionally, your maintenance costs will be much higher with metal halide and fluorescent lights compared to LEDs. If you replace a metal halide light only when it burns out, you will have replaced that one light at least two times in the time it takes for the LED to reach 70% of its original lumen output.

When it comes to replacing your existing lighting system, it is important to take into account the light output and how long it will last.

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