In the lighting industry, we can usually find those words: luminous efficiency, efficiency of lamps and lanterns, the whole light effectiveness, efficiency and effectiveness…Do you know what they are?
Luminous efficiency represents how much light/lumens you get for a specific amount of energy watts. The unit of it is lumens per watt（lm/ W）, luminous efficiency is a very important standard to consider whether a bulb is energy-saving or not. The higher the luminance efficiency is the more economic the bulb will be. As the development of science and technology, the luminous efficiency of LED bulb is keep improving.
In some systems of units, luminous flux has the same units as radiant flux. The luminous efficacy of radiation is then dimensionless. In this case, it is often instead called the luminous efficiency, and may be expressed as a percentage. A common choice is to choose units such that the maximum possible efficacy, 683 lm/W, corresponds to an efficiency of 100%. The distinction between efficacy and efficiency is not always carefully maintained in published sources, so it is not uncommon to see “efficiencies” expressed in lumens per watt, or “efficacies” expressed as a percentage. (Source from Wiki.com)
The luminous efficiency standard of some common light sources
1. A 60w incandescent bulb, the lumen is 806, so the luminous efficiency is 806lm/60W about 13 lm/W.
2. An energy saving bulbs’ luminous efficiency can be classified to three levels. The first level is the best.
3. The energy saving bulbs of 15W-24W, the first level of the luminous efficiency should at least be 69lm/w, the second level should at least be 61lm/w and the third level should at least be 51lm/w.
The Luminous Efficiency of light source, Luminaire Efficiency and Luminaire Efficacy
1. The unit of luminous efficiency of light source is lm/w, different light source have different luminous efficiency values.
2. Luminarie efficiency： If we add some lighting fixture around the light source, with the reflector, lens or some other fixtures, the luminous efficiency must be very different and must be lower than luminous efficiency of light source.
The output light ratio of lighting fixture is the Luminarie efficiency. It’s the ratio of the output lumen of lighting fixture and the output lumen of light source in the lighting fixture.( The unit is lm/lm)
3. Luminaire efficacy: It means the efficiency of the whole light. It’s the ratio of the output lumen of the whole light and the consumed power. (The unit is lm/w).
Efficiency and Efficacy
Efficiency and efficacy are different.
Efficiency is a ratio, it’s lm/lm, for example, the efficacy of LED light is about 0.66-44%.
Efficacy is lm/W, for example the efficacy of LED light is about 60-90lm/w.
What kind of lighting fixture got the best luminous efficiency?
|luminous efficiency of light source||Power Efficiency||effective illumination efficiency||lighting fixture efficiency||Luminous Efficiency of the whole light|
From this form, we can know that luminous efficiency of LED lighting fixture is much better than fluorescence lighting fixture, HPS and Traditional lights (Tungsten light, incandescent bulbs and so on.)
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