What is CLO - Constant Lumen Output?

Date February 08, 2022
Categories Knowledge

Constant Light Output (CLO) is a system to compensate for lumen depreciation and to avoid excess lighting at the beginning of the installation’s service life. 

First, let's understand lumen depreciation. When an LED light is first turned on the LED chips are running at peak performance. Over time they become less effective, and the light output decreases. This happens very slowly, in fact, so slowly the human eye won't normally notice. That is until the light reaches 70% of its original capacity, in which you would expect to replace the light. The industry standard has become known as L70 (lifetime at 70%). Typically a light will reach L70 somewhere between 50,000 - 100,000 Hrs. 

For many years, Lumen Depreciation has been compensated by putting extra light in at the start. Typical Light performance looks like this:


Enter CLO! With a simple, yet very smart technology, you can now have a constant light output for many years. CLO performance looks like this:


CLO (Constant Light Output) is a function provided by programming a compatible power supply. By loading in a COT file (Command-over-time) the power output will incrementally increase over a set amount of hours, usually 70,000 hours. The COT File is a script that is loaded onto the driver usually with NFC (Near Field Communication) technology.

Benefits of CLO:

  • Better thermal management of LED, extending the lifetime
  • Power consumption control, providing cost savings
  • Set-and-Forget, no maintenance or further programming is required

To summarise, when using CLO Technology, lights will last longer, cost less to run, and over the life of the installation, there will be no discernable difference in lumen output.

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