Deciphering LED Metrics

LED metrics

Inside LED Metrics

Buildings, January 29, 2016. Image credits: Lee_seonghak

Lighting Facts Labels
The DOE established the LED Lighting Facts program to ensure one consistent source of information about all LED products. Lighting Facts labels include five basic metrics.

Color temperature (CCT): Color temperature characterizes how “cool” (blue) or “warm” (yellow) a white light appears. Ratings are expressed in Kelvins (K). Lower numbers around 2500-3000K indicate warmer light, mid-range values of 3500-4000K are generally considered fairly neutral and white, and higher temperatures appear cooler.

Watts: Lighting Facts labels also provide the input wattage of the lamp. Use it to project energy savings based on the lighting system you’re replacing with LEDs.

Efficacy: Expressed in lumens per watt, the efficacy rating denotes how much light the product puts out for every watt of electricity it uses.

Useful life: Lifetime ratings represent approximately how many hours of operation it will take before the LED’s light output has declined to 70% of the initial lumens, referred to as lumen maintenance and often abbreviated as L70. The DOE recommends asking the fixture manufacturer for test data to support the life claims on the package.

Expected lumen maintenance: The calculated L70 value sometimes exceeds the intended product use cycle or the lifetime of another lighting system component, the DOE explains. An alternative method of calculating lumen maintenance performance involves predicting what the lumen maintenance will be at a fixed time interval, such as 25,000 hours.

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