From one perspective, the language and terminology that describes LED lighting will sound as if it were drafted by an accomplished science fiction writer. This is particularly true when that terminology is compared to traditional lighting technologies that are characterized almost entirely in terms of watts, ballasts, and frosted or clear globes. Although it may sound as if it includes discussions of flux capacitors, the language of LED lighting is neither complex nor confusing, and understanding a few key LED language terms will help you to make the most intelligent purchasing decisions.
Lighting Efficiency and Lumen Ratings
The lighting efficiency and lumen rating of an LED bulb are interrelated, and these values represent the primary difference between LED and more traditional lighting that is rated in terms of wattage. More purchasers are generally aware of how much light a 60-watt incandescent bulb will generate, but that wattage rating is more of a measure of the bulb’s power consumption than it is of its light-generating capability. That capability is more appropriately measured in terms of the bulb’s illuminance, which is its ability to generate a defined amount of light per each watt of input power. LED lights are up to ten times more efficient than incandescent fixtures, and while an incandescent bulb, for example, might have a lighting efficiency of only 12 lumens per watt, an LED bulb might generate up to 120 lumens per watt.
What is a Color Coordinated Temperature (CCT)?
Understanding an LED light source’s color coordinated temperature (CCT) will also be important to appreciate whether the light will appear to create a warmer or cooler lighting atmosphere. A light source’s CCT is measured in degrees Kelvin. Somewhat conversely, LED bulbs with higher Kelvin temperature ratings will generate light that is perceived to be cooler and brighter, whereas bulbs with lower CCT ratings will seem warmer. Typical Kelvin temperature ratings of LED bulbs range from 2700 Kelvin, which is perceived to be warm white light, up to about 7500 Kelvin, which is cool white light.
You likely understand that colors might appear to be different under different types of light sources. An LED light source’s color rendering index (CRI) is a relative measure of how well that source replicates bright, natural sunlight. Natural light and some incandescent bulbs can render colors most accurately, and accordingly have a CRI of 100. LED bulbs generally have CRI ratings of between 70 and 95. If you are using LED lighting in areas where you want colors to appear most naturally, look for LED bulbs that have higher CRI ratings.
What Does “L” and “LM” on a lightbulb mean?
You might also see “L” or “LM” ratings for LED bulbs. A modern LED bulb can perform at a high level for more than 50,000 hours of use, and in some cases more than 100,000 hours. Unlike incandescent bulbs, however, LED bulbs will generally not fail suddenly, but instead the quality and quantity of their lighting will recede over time. An LED bulb rated as “LM70 50,000 Hours” will generate at least 70% of its initial lumen rating for at least 50,000 hours of use. Naturally, higher-quality LED bulbs will have higher LM ratings.
The common language of LED bulbs includes many other terms, such as drivers, white- and color-dimmable, and omni-directionality. This terminology reflects the exciting possibilities of LED lighting technology.