Lumens: How to Compare Light Output Between Different Lighting Technologies
You know how much light to expect from a standard 4-foot fluorescent tube, but how do you determine how bright a 18-watt LED tube is? Enter lumens.
Lumens are the measure of total light intensity from a single source (in this case, a tube). The greater the lumens, the brighter or more intense the light. A 40-watt fluorescent tube, for example, is rated around 2300 lumens. To replace it with the same intensity LED, just look for one that rates around 2300 lumens.
Of course, not every fluorescent, incandescent, metal halide, etc., lamp will give its lumens. Here is a chart to help you come up with a rough calculation on your own, to make it easy to compare to LED lights (which always have a lumen value as part of their specifications). Simply multiply the average lumens per watt by the number of watts.
|Light Type||Average Typical Luminous Efficiacy
|Metal Halide||87.5 lm/W|
|High pressure sodium||117.5 lm/W|
|Low pressure sodium||150 lm/W|
|Mercury vapor||50 lm/W|