light-emitting diode or LED is a semiconductor light source used as indicator lamps in electronic devices and as energy efficient lighting. Invented by the “father of the light-emitting diode” Nick Holonyak while working as a consulting scientist at a General Electric Company laboratory in Syracuse, New York in 1962. LEDs have transformed the world of portable lighting by virtue of their efficiency and longevity.

Source: Wikimedia Commons. Author: Afrank99.

Modern LEDs can be anywhere from 3 to nearly 10 times as efficient in terms of light generated per unit of power consumed in comparison to traditional incandescent light sources. Whereas traditional 100 watt incandescent light bulbs generate roughly 17 lumens per watt (lm/W), the most efficient LEDs can generate over 160 lumens using the same amount of electricity.

For low power portable lighting applications such as flashlights and bicycle lights, the benefits can increase by a further 3 fold. This is because incandescent lighting becomes less efficient at lower power ratings, whereas LEDs are conversely more efficient at lower power. For instance, an incandescent 5 watt bulb will produce roughly 5 lumens per watt for a total of 25 lumens. At the same 5 watts, today’s top LEDs produce roughly 25 times as much light at 600 lumens with an efficiency of 125 lm/W!

Old Growth Redwood

SourceFlikr: The Commons. Photographer: Rupak Shrestha.

In comparison to incandescent lighting, LEDs have amazing potential lifespans measured on the order of multiple YEARS of uninterrupted 24-hours a day seven days a week operation. However, early producers of LED lighting products naturally treated LEDs like the incandescent lighting they were accustomed to working with meaning that they did not pay sufficient attention to heat dissipation and/or incorporating LED specific electronic drivers able to provide the very stable current needed to prevent LEDs from being damaged. This resulted in many LED products failing much earlier than anticipated.
A quality LED provided with sufficient cooling and stable current will not “burn out” even after well over a decade of service. Instead, LEDs grow progressively dimmer over years of use. In the past, manufacturers faced a quandary as to how to specify the lifespans of their products. In recent years, a general consensus has formed around defining the “service life” of an LED in terms of hours of continuous operation before brightness drops to 80% of new. Top LEDs have recorded service lives under this measure of up to 50,000 hours or over 5.7 years of uninterrupted operation! Quality LEDs operating in well-designed products can be expected to retain 95% of their brightness after a full 1.5 years of continuous operation according to manufacturer data.


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