For a long time, many people determined the brightness of a light bulb by looking at its wattage. The assumption is that a 100-watt light bulb, for example, is naturally going to be brighter than a 40-watt bulb.
While that works for incandescent bulbs (although, even then, it is an imprecise way of measuring brightness), with the development of low-energy LED light bulbs, the wattage alone will not necessarily indicate how bright a bulb is. There are some better ways to tell, though...
Equivalent wattage
The reason you can no longer use watts to determine a light bulb's brightness is because LED bulbs offer the same light as incandescent bulbs, but they have a much lower wattage. Below is a rough guide to the equivalent wattages of LED and other bulbs.
What are lumens?
Lumens (lm) are a measure of the amount of visible light that a lamp or other light source emits. It is a much more accurate way of determining a bulb's brightness, as it is a measure of its output, unlike the wattage, which just denotes the power input.
LED light bulbs for general use around the home will typically have a wattage between 5W-15W, and will emit between 300-500 lumens. Some outdoor floodlights emit in excess of 20,000lm.
Lumen to watt ratio
LED bulbs that have the same wattages might not necessarily have the same lumens ratings. For example, a particular 5W GLS might emit 400 lumens, while another one might emit 470 lumens.
The simplest way to measure the efficiency of an LED light bulb is to calculate its lumens to watt ratio. To do this, just divide the number of lumens it emits by its wattage: for example, a 5W bulb that emits 400 lumens has a ratio of 80 lumens per watt (abbreviated to lm/w).
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Now, let's delve into the concepts discussed in the article titled "How Bright are LED bulbs?"
Equivalent Wattage: In the past, people commonly gauged the brightness of a light bulb based on its wattage. However, with the advent of low-energy LED bulbs, this method becomes imprecise. LED bulbs provide the same brightness as incandescent bulbs but with significantly lower wattage. The concept of equivalent wattage helps bridge this gap, offering a rough guide to the wattage of LED bulbs that would produce similar brightness as traditional incandescent bulbs.
Lumens: The article rightly emphasizes that lumens (lm) are a more accurate measure of a bulb's brightness compared to wattage. Lumens quantify the amount of visible light emitted by a lamp or light source. LED light bulbs designed for general home use typically have wattages ranging from 5W to 15W and emit between 300 to 500 lumens. This shift to lumens provides a more precise understanding of a bulb's brightness as it directly measures the light output rather than the power input.
Lumen to Watt Ratio: The efficiency of an LED light bulb is best measured by its lumen-to-watt ratio. This ratio is calculated by dividing the number of lumens emitted by the bulb by its wattage. For example, a 5W LED bulb that emits 400 lumens has a lumen-to-watt ratio of 80 lumens per watt (abbreviated to lm/w). This metric is crucial for assessing the efficacy of LED bulbs and comparing their performance, as two bulbs with the same wattage may have different lumens ratings.
Understanding these concepts—equivalent wattage, lumens, and lumen-to-watt ratio—is essential for consumers to make informed decisions when choosing LED bulbs for their homes. These metrics provide a more accurate and standardized way to evaluate the brightness and efficiency of modern lighting solutions.
