When learning about LEDs (Solid State Lighting) you have come to the right place. Lighting companies have been testing/using LEDs for over a decade and are the best source for information. You wouldn’t buy your next laptop from your grocer, would you?
Here is some general information about LED’s as would be asked by specifiers or end-users. Some questions are generated from media articles, some from marketing materials put out in the market and some from energy consultants (LEED, Greenbuild, etc). Knowing how to answer these can make YOU the lighting expert and can assist in making sure the right product is used.
How Long Does an LED Last?
The life of an LED is dependant on the engineering of the product it is in and the environment in which it is meant to operate. The exact same LED chip can last 500 hours in a poorly-designed product and over 50,000 hours in a well-designed product. The key factor is how quickly the heat-sync can get the heat away from the LED. An LED is typically considered “dead” at 70% of initial light output. A quality product that offers 90 foot-candles of illumination will still provide 60+ foot-candles 20-25 years from now (an 8-10 hour/day office environment).
Should Motion Sensors be Used with LED Task Lights?
Since most LED task lights operate at under 13W, the benefit of using a motion sensor does not necessarily outweigh the additional cost. In addition, motion sensors provide an “active” power draw which decreases the overall efficiency of the product. The motion sensor also provides one more complicated component which can fail and, if it is hard-wired into the fixture, can require replacement of the entire fixture if it fails.
Should the LED be Replaceable?
A good product with a good warranty will last you 20+ years in a standard office environment. There will be no way to obtain the same LED technology for replacement this far down the road (LED technology changes very quickly as do the components used to “drive” them). If the product offers replaceable LEDs it is likely due to the fact that they will NEED to be replaced within the warranty period. This is often a sign of low confidence in the longevity of the product. Replacement LEDs are seen mostly in flashlights, automotive and low-cost residential applications where the price-point precludes the quality and engineering necessary to ensure proper heat-syncing.
What is the Incandescent Equivalent of an LED?
LED light sources, and Solid State Lighting in General, is a unique light source and cannot be directly correlated to an Incandescent light source. Incandescents emit visible light 360 degrees from the light source and LEDs only 180 degrees. The most important factor is where you put the light. Most incandescent A-lamp style products utilize a painted reflector housing where more efficient Halogen fixtures utilize polished aluminum reflectors to direct the light onto a task plane (ie. worksurface). LEDs require sophisticated optics between the LED and the task plane to accomplish the same feat. Incandescent sources produce U/V light, IR light and Visible light. LED’s produce only visible light and are therefore more efficient. A good-quality LED will place 90% of the light generated onto a task plane at 18”. LED task lights must cover a worksurface large enough to be the sole-source of task lighting.
CRI - The accuracy of the color of a light sensor is often measured in CRI, or Color Rendering Index. Incandescent light sources have a CRI of 100. A good quality LED should have a CRI between 82 and 92CRI (a very good approximation of natural light). TEST – Hold your hand under the lamp. If your skin turns grey while placed under an LED light source, it has poor color rendering (not enough of the red and yellow spectrums represented in the phosphors being used in LED production).
What is the fluorescent Equivalent of an LED?
Since fluorescents have been around for 40+ years there is a definite correlation between fluorescent and incandescent. 13W of fluorescent, in a well-designed fixture with quality reflectors, can equate to 60W of incandescent light (see Incandescent Equivalent answer). The most popular and cost effective fluorescents will provide Color Rendering (CRI) between 72 and 82. This is lower than most quality LEDs. If you are looking at an LED product that draws in excess of 13W, you are generally better off with Fluorescent as it will take 10-15 Watts of LED to accomplish the same light output.