Are LED Bulbs Brighter Than CFL Bulbs?
Lumens: Why you can’t use them to compare LED Bulbs to traditional bulbs
Are LED’s brighter than Compact Fluorescent (CFL) bulbs? Some people say that LED’s still aren’t as bright as Compact Fluorescent bulbs. Some people say you should switch to LED’s RIGHT NOW because they’re way more efficient. So what’s the real answer? It depends…this article will explain why.
There’s a push now towards “green” technology – alternative energy and finding ways for us to reduce our carbon emissions and reduce our dependency on foreign oil. One of these technologies is LED lighting.
LED’s give directional light. This is unlike incandescent, halogen or compact fluorescent bulbs that give out omni-directional light (or light all around the bulb). The way that’s normally been used to measure the efficiency and brightness of these bulbs is the lumen. You’ve probably heard of it or seen it on packaging. Another measurement is lumens per watt. Both of these measurements are poor ways to compare the brightness of LEDs to other types of bulbs (CFL, incandescent & halogen).
LED Terminology
First off we need to clarify come terms:
What is a lumen?
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| You’ll typically see lumens shown on packaging for a CFL Bulb. |
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| Source: http://www.led.net/pages/tech4.htm
In everyday terms, lumens is measured by taking a lumen measuring device and taking the average of the lumen rating all around a light source. |
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| This is called an integrating sphere – and is used to measure the lumens of a bulb. |
What is a footcandle/lux?
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| In everyday terms, a footcandle/lux is a measurement of light at one point. It’s taken with a light meter. |
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| The higher the measurement the “brighter” the light is at the point measured. |
Luminous efficacy or lumens/watt
“Luminous Efficacy” is a way to measure the amount of light you get for the amount of energy you put in. You take the total # of lumens and divide it by the wattage of the light bulb (lumens/watt). Here’s a comparison of incandescent, CFL’s and LED’s at the moment.
Looks like CFL’s are more efficient than LED’s right? Wrong.
Fixture efficacy
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In certain fixtures, an LED bulb actually gives out MORE light or is more efficient than CFL bulbs.
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| In this diagram, about half the light the CFL bulb is giving off is actually wasted and is reflected back in to the ceiling while with the LED, ALL the light is directed downwards where it’s usable. | |
So in this case, the efficacy of the bulbs while they are INSIDE the fixture -
For LED’s: 57 lumens per watt (lm/W)
For CFL’s: is reduced from 61 lumens per watt to 30 lumens per watt (lm/W) since half of the light is wasted.
Conclusion
So are LED bulbs brighter than CFL bulbs? In a recessed fixture, YES. Since ALL the light from an LED bulb is used in these, while a CFL bulb loses about half the amount of light it actually puts out (LED’s have higher fixture efficacy). In something like a floor lamp where you need the light spread to be much larger (all around the bulb) then CFL’s, at the moment are still more “efficient”. 100% of the light they put out is used. (CFL’s have higher fixture efficacy)
So what’s the best way to measure brightness?
There’s currently no standardized way of measuring LED bulbs that are used to replace traditional bulbs. The US Department of Energy and 3rd party organizations like Energy Star are trying to come up with ways to do so – but things like these take time.
As a result, many people are stuck with manufacturer’s overstated claims and are many times burned (no pun intended) when buying LED bulbs by not getting the amount of light they were expecting. Also a lot of people are just looking at the total lumens that a bulb outputs. This was great when we were only comparing incandescent and CFL’s, but with LED’s as explained, the LED’s use mostly ALL their light in a recessed fixture, while a CFL wastes a lot of light.
Until standards are finalized, if you want to buy an LED bulb and want to get what you pay for, rather than just guessing do the following:
Ask for side by side pictures of the bulb that is being replaced as well as getting footcandle measurements (with a light meter) for both (if possible). This will show and tell you that the LED bulb is giving the brightness and color that you’re expecting as well as the beam spread (the 3 most important factors of an LED bulb).
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For a wide-range of LED light bulbs, that come with a two-year warranty, from flood lights to globes with picture comparisons and detailed payback periods by state, check out our online store at: http://www.eternaleds.com/.
Jeff Chan
Eternaleds Inc.
Posted 11/24/08