As discussed in Part I of this guide to LED Lighting having a full understanding if the terms used in today’s lighting is very important to electrical contractors. It will help you in the selection of product, buying LED fixtures, and securing business. When it comes time to speak with specifiers, end-users, and General Contractors, how well you understand the technology definitely plays a role in securing new business

When you can make suggestions to improve the quality of the job or reduce the cost, this will always make your firm a top contender when it comes to bid time. It all comes down to fully understanding the terms – and what they mean today. Some of the meanings have definitely changed over the last 5-10 years.

Below your will find a list of the most critical terms. A much more extensive list can be found at Lumight’s Glossary of lighting terms 



Smart girl surrounded with stacks of books reading dictionary



Learn LED Terms and Specifications


  • Lumen – A lumen is a unit measuring the amount of visible light emitted by a light source.
  • Lux – A lux is a unit measuring luminance in an area; one lux is equal to one lumen per square meter of space.
  • Lumens Per Watt (LPW) – The LPW of a light source measures how efficiently the source creates light given the amount of wattage provided. In other words, the LPW measures how many lumens are created for every watt consumed.
  • Footcandle – A footcandle is a unit of luminance used widely in the United States. One footcandle is equal to one lumen per square foot, or about 10 lux (lumens/square meter).
  • LED Wattage – The amount of power drawn solely by the LEDs. LEDs are more energy efficient than traditional light sources and require a lower wattage to produce the same amount of lumens.
  • System Wattage – The system wattage refers to the wattage drawn by the entire fixture, including the LEDs and any drivers/transformers that are part of the fixture.
  • Color Temperature – The color of light generated.
  • CCT (correlated color temperature) – The correlated color temperature is the measurement of a light's relative coolness (blues) or warmth (yellows). A light source's CCT refers to the temperature (in degrees Kelvin, or 'K') that a blackbody would have to be to radiate light of the same hue, or color. Imagine a piece of metal thrown into your campfire—as it gets hotter, it glows different colors. This is a rough approximation of how CCT works.
  • Blackbody – A blackbody is a theoretical or ideal object that absorbs all electromagnetic radiation (EMR), thus appearing black in color. As the blackbody heats up, it glows different colors.
  • CRI (Color Rendering Index)CRI refers to the ability of a lamp to accurately reproduce the colors of an object as they would appear in noontime sunlight. It's measured on a scale from 1 to 100, where 100 is the sunlight—the higher the number, the better the light source renders colors.
  • Rated Life – The rated life of an LED is the average amount of time it takes for the lamp to generate 30% less light than it did originally.
  • DLCDesignLights Consortium. DLC is a regional non-profit with the intention of promoting energy efficiency. It publishes the Qualified Products List (QPL) which lists certified product information, including verified tested performance and rated performance information.
  • LM-79 – The LM-79 is a benchmark that shows consumers the advantages of a LED fixtures/systems over other lighting options. It measures an entire fixture's performance including its total luminous flux, luminous intensity distribution, electrical power, efficacy (lumens per watt delivered), and color characteristics (chromaticity, CCT, and CRI).
  • LM-80 As LEDs have no filament to burn out, they reach the end of their life span differently than incandescent, slowly losing light quality until becoming unusable. The LM-80 measures an LED emitter's rate of lumen depreciation and other general characteristics (only the emitter is measured, not the fixture).
  • Theoretical Life – While an LED's usable or rated life is measured by how quickly it loses 30% of its luminosity, it will rarely “die” and continues to produce some light almost indefinitely. The theoretical life of properly maintained LEDs with good thermal management can be as high as ~350,000 hours.
  • Thermal Management – LEDs are more efficient than traditional lamps, but to maintain their efficiency, long life, and color temperature, they must be kept cool with good thermal management. Many techniques (like utilizing heat sinks or thermally conductive adhesives) exist to help wick the heat away from the LED emitter.
  • Driver – LEDs require a specific current at a specific voltage to operate correctly; a driver is an electrical device which maintains this. Typically, LEDs require DC and drivers also provide the function of rectifying AC current into DC current.
  • Emitter – An LED's emitter is, as one would expect, the part that emits light. It is the “LED” only. In contrast to previous forms of lighting, the LED emitter is not a bulb containing a filament or gas, but a semiconductor diode.
  • Dimming – LEDs can be dimmable light sources when paired with an appropriate dimming driver. This is important to keep in mind considering the increasing importance placed on energy efficiency and “smart” controls.
  • RGB – Some LEDs can change colors and are typically referred to as RGB LEDs. The RGB model of color uses combinations (and dimming) of Red, Green, and Blue light to create a wide array (including white and 16 million+ others) of hues.


Part I of this series

Part III of this series



  • 200W
  • Bronze