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Lumens vs. Watts for LED Bulbs

by Aaron Ziv, Demand Media

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Like all lightbulbs, light-emitting diodes (LEDs) produce illumination by turning a given amount of electric current into light. LEDs perform this conversion more efficiently than standard incandescent bulbs: According to the U.S. Department of Energy, a typical Energy Star-rated LED uses 20 to 25 percent of the energy that an incandescent bulb uses; the LED lasts up to 25 times longer, too (see References 5). The amount of light a bulb generates can be measured in a unit called lumens. Electrical power is measured in a unit called watts. Due to their methodology of converting electricity into light, LED bulbs feature a higher ratio of lumens to watts than incandescent bulbs.

Lumens

A lumen is a measurement of light directly relevant to human beings. Instead of trying to measure the number of photons or raw radiated energy, the lumen scale describes the amount of light, or brightness, that the human eye perceives. All modern lightbulb packaging shows the number of lumens the bulb produces. An average 100-watt incandescent bulb, for example, produces about 1,600 lumens. (See References 2.)

Watts

A watt is a measurement of electrical power, formally equal to the amount of energy in 1 ampere of current flowing at 1 volt. A lightbulb that is rated at, say, 200 watts uses more electricity to produce light than a bulb rated for 100 watts. The benefit, however, is that the 200-watt bulb produces significantly more light than the lower-rated bulb. The relative efficiency of different lightbulbs can be gauged by comparing how many lumens they produce for every watt of electrical power.

Watts and Lumens in LEDs

LEDs that are bright enough to replace incandescents for household use---that is, producing the same number of lumens as standard 40- or 60-watt bulbs---typically only use 9 to 12 watts. The U.S. Department of Energy advises that consumers who want to replace a 60-watt bulb should look for an LED that produces close to 800 lumens; for a 40-watt bulb, look for 450 lumens (see References 2). As of March 2011, manufacturers were just starting to produce high-powered LEDs for the home. Philips has developed a 60-watt replacement that only uses 12 watts of power (see References 7), while GE has developed a 40-watt replacement that uses only 9 watts of power (see References 4).

Light Quality

Lumens don't describe the quality of the generated light---its color, tone or other variables. Some people find they don't like the light that certain LED bulbs produce, describing it as "cold," "pale" or "dim." The biggest challenge for LED manufacturers is creating bulbs that mimic conventional ones in shape and light quality. As of March 2011, compact fluorescent lamps (CFLs), which use 25 percent of the energy of standard incandescents, were still more versatile and cost-effective than LEDs (see References 3).

How LEDs Work

When electrical current runs through an LED, the electrons in the current flow into a semiconductor material containing electron "holes"---spaces waiting to be filled with electrons. When the electrons fill those holes, energy is released as photons, or light that is emitted outward, turning the LED into a lightbulb. In contrast, incandescent bulbs generate light from the electrical resistance of a metal filament. The resistance method requires more electrical energy to heat up the filament to a point that it glows and emits light. (See References 6.)
About the Author
Aaron Ziv has been a writer and photojournalist for 10 years in Washington, D.C., and the Middle East. A student of political science and psychology from the University of Maryland, he also does technical and market analysis for a green technology company. His work has appeared in local newspapers, commissioned research and a patent or two. He began writing professionally in 1998.
Photo Credits
  • Kiyoshi Ota/Getty Images News/Getty Images
Source: http://greenliving.nationalgeographic.com/lumens-vs-watts-led-bulbs-2789.html

Lumens vs Watts

Lumens vs Watts

What are Lumens?

Watts measure the amount of energy required to light products, whereas lumens measure the amount of light produced. The more lumens in a light bulb, the brighter the light.
For instance:

FTC's Lumen vs. Watts Chart
  • 40-watt incandescent bulb = 450 lumens
  • 60-watt incandescent bulb = 800 lumens
  • 100-watt incandescent bulb = 1600 lumens
With new light bulbs, shopping by lumens will be more important than shopping by watts when choosing which energy-efficient bulb to purchase.

New Labels


The Federal Trade Commission has worked with manufacturers to develop a new label to help consumers purchasing the energy-saving bulbs. It looks similar to nutrition labels on food and will have more concise information about the bulb’s output and savings (seen in the image on the right).
The labels will include:
  • Brightness (in lumens),
  • Estimated Yearly Energy Cost,
  • Life-expectancy of the bulb,
  • Light appearance and,
  • Energy used.

Click here for a larger version of this new label breakdown from the NRDC


Manufacturers are also changing the look of their overall packaging to help even more. For instance, the CFL in the photo on the right says the Sylvania Super Saver CFL is a replacement for a 100 watt bulb with a lumen (brightness) output of 1500. The energy used is 24 watts, saving you $60 in energy costs and will last for 7 years. The color is a soft white, which is similar to soft white incandescent bulbs.
Remember, an easy way to compare bulbs is to use the government label, which should appear on all bulbs by January 2012.

Learning About Labels

Source: http://lumennow.org/lumens-vs-watts/

There seems to be some confusion about how to tell how bright a light bulb really is. It was easy enough when we all used incandescent lights. You could choose from a 40, 60, 75 or 100 watt bulb, and we all have a rough idea of how bright that will be.
When you begin to get into new lighting solutions like CFLs and LEDs, using the wattage doesn’t work very well any more. Now you have 20 watt CFLs, and 12 watt LEDs and no idea what's going to keep you from going blind while reading. Well, read on and learn how to tell how bright something actually is. Before you lose your eyesight. 

Just Look to the Lumens
A Lumen is standard unit of light as it is perceived by the human eye. Essentially, it will tell you how bright something is, unlike a watt, which is actually a measurement of energy consumption or output. The lighting industry has standardized ways that it measures the total emission of light from a product and include it on most packaging. Here’s  the lumens from some everyday objects to give you a better idea.
  • 40 watt incandescent = 380 – 460 Lumens
  • 60 watt incandescent = 750 – 850 lumens
  • 75 watt incandescent = 1100 – 1300 lumens
  • 100 watt incandescent =  1700 – 1800 lumens
  • Direct sunlight = 100,000 lumens.

One of the reason LEDs are so attractive is that with a fraction of the power use (watts) you can get the same amount of light (lumens) as an incandescent.

You can get as many as 110 lumens per watt with an LED bulb. Compare that to an incandescent, which only produces 12-17 lumens per watt. Now that’s some science that can save you money. 
Check out some of our other articles if you want to learn more about how an LED light bulb works.
How much wattage do you like in your home? Did you use 60 or 75 watt lights?

How to convert lumens to watts

How to convert luminous flux in lumens (lm) to electric power in watts (W).
You can calculate watts from lumens and luminous efficacy.  Lumen and watt units represent different quantities, so you can't convert lumens to watts.

Lumens to watts calculation formula

The power P in watts (W) is equal to the luminous flux ΦV in lumens (lm), divided by the luminous efficacy η in lumens per watt (lm/W):
P(W) = ΦV(lm) / η(lm/W)
So
watts = lumens / (lumens per watt)
or
W = lm / (lm/W)

Example

What is the power consumption of a lamp that has luminous flux of 900 lumens and luminous efficacy of 15 lumens per watt?
P = 900lm / 15lm/W = 60W

Luminous efficacy table

Light type Typical
luminous efficacy
(lumens/watt)
Tungsten incandescent light bulb 12.5-17.5 lm/W
Halogen lamp 16-24 lm/W
Fluorescent lamp 45-75 lm/W
LED lamp 30-90 lm/W
Metal halide lamp 75-100 lm/W
High pressure sodium vapor lamp 85-150 lm/W
Low pressure sodium vapor lamp 100-200 lm/W
Mercury vapor lamp 35-65 lm/W

Lumens to watts table

Lumens Light bulb
watts
Fluorecent
 / LED
watts
375 lm 25 W 6.23 W
600 lm 40 W 10 W
900 lm 60 W 15 W
1125 lm 75 W 18.75 W
1500 lm 100 W 25 W
2250 lm 150 W 37.5 W
3000 lm 200 W 50 W

Watts to lumens calculation ►


See also

Source: http://www.rapidtables.com/calc/light/how-lumen-to-watt.htm

Lightbulb Watt-to-Lumen Conversion Guide

We all know how much light a 60-watt bulb will produce. But the brightness of new CFL and LED lightbulbs are measured in lumens, not watts,  so here's a chart to help you do the conversion.

How Much Light Do I Need?
Incandescent Bulbs
WATTS
Minimum Light Output
LUMENS
40 450
60 800
75 >1,100
100 1,600
150 2,600

More info: Lightbulb brightness in general is measured in lumens (not watts). Light bulb manufacturers include this information and the equivalent wattage right on the packaging. Common terms are "soft white 60," "warm light 60," and "60 watt replacement."
To save energy, find the bulbs with the light output you need, and then choose the one with the lowest wattage. You can also look for an ENERGY STAR qualified bulb that is labeled as equivalent to the incandescent bulb you are replacing.
The color of light may also affect how bright a light appears, even if the lumens are the same. Since most people are used to the soft yellowish glow from incandescent light bulbs, ENERGY STAR qualified bulbs that produce light closer to the color of daylight (color temperatures above 3000K) may appear brighter because the color of the light is less yellow. 
Source: Energystar.gov

Lumens Vs. Watts








The lumen and the watt are both units of measurement. The lumen is a measure of light while the watt is a measure of power. Does this Spark an idea?



  1. What is a Lumen?

    • Lumens are a measure of the perceived power of light -- i.e. of light you can see. Waves of light that are beyond the spectrum visible to the human eye are not included in the lumen.

    What is a Watt?

    • A watt is defined as the amount of power needed to move a one kilogram (2.2 pound) object at a speed of one meter per second against a force of one newton. In simple terms, it is a measure of the amount of energy something either uses or produces. One watt is equal to 1/746 horsepower.

    What is the Difference?

    • Because watts and lumens are measures of different things, there is not necessarily any correlation between them. For example, a conventional light bulb and a compact fluorescent light bulb may put out the same number of lumens, but the conventional bulb will consume three to five times the number of watts needed by the compact fluorescent.

    An Increasingly Common Term

    • Lumens have come into everyday use largely as a result of the government mandate to phase out incandescent light bulbs in favor of compact fluorescents. Because the two types of bulb consume different amounts of power to produce a given amount of light, lumens offer an easier way for consumers to compare the new lightbulbs with the older ones they are replacing.

    Origins of the Terms

    • "Lumen" comes from the Latin word for "light." The "watt," however, is named in honor of James Watt (1736-1819), a Scottish inventor, in recognition of his contributions to the development of the steam engine.

Energy-Efficient Lighting: Lumens vs. Watts

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Author(s): 
Allyson Schmutter
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As the Federal Trade Commission (FTC) and lighting manufacturers place more information on light bulb packaging, it’s important to learn the difference between watts (the old way of labeling bulbs) and lumens (the new way).

 What's a Watt?

Watts measure the amount of power a bulb uses – not how bright it is. So, using watts to describe brightness is like using gallons of fuel to describe how fast a car can go.This practice wasn't a problem as long as we continued to use the more than 100-year-old incandescent bulbs.
The problem: Traditional incandescent light bulbs waste 90% of their electricity to produce heat, and use only 10% to produce light. The solution: energy-efficient bulbs, which use fewer watts to give off the same amount of brightness.
As more consumers buy energy-efficient bulbs, labels on bulb packages are using a more accurate measurement of brightness: lumens.


Look for Lumens

Lumens measure the amount of light produced by a bulb. The more lumens in a light bulb, the brighter the light
The FTC’s conversion chart shows how lumen measurements match up to the old wattage amounts (see image on the right).
For example:
  • 40-watt incandescent bulb = 450 lumens
  • 60-watt incandescent bulb = 800 lumens
  • 100-watt incandescent bulb = 1600 lumens

More on Lumens vs. Watts

  • FTC video: How to look for lumens when buying bulbs

New Labeling Tips

Source: http://www.ase.org/efficiencynews/energy-efficient-lighting-lumens-vs-watts

Goodbye, Watts. Hello, LUMENS!

May 17, 2012 - 2:21pm
For years, I bought light bulbs based on watts, or energy use. Like many light bulb consumers, I looked for a traditional 40, 60, 75, or 100 watt incandescent bulb. Now that stores today carry more and more energy efficient lighting choices, I wanted to replace my old incandescents with new bulbs to save energy and money on my electricity bill. But in shopping for the right bulb, I came across a challenge in looking for bulbs based on watts. Since these newer bulbs use less energy, I found bulbs that use 8, 15, or 26 watts. The wattages are pretty close to each other, but the brightness levels of each of these bulbs can vary a lot! Sound confusing? No worries. Read on, because there is a light at the end of this tunnel (pun intended)…

So, all I wanted to do was to find a light bright enough for my bathroom so I don't get cut shaving in the morning. I realized that the best way to shop for light was to look for the brightness, or lumens, of the bulb, instead of the watts. Lumens tell you how bright a bulb is, and are listed on the bulb packaging. More lumens mean brighter light. When replacing a 60-watt traditional bulb, you should look for a new bulb that gives you about 800 lumens.

The Energy Department has some informative resources to educate consumers on lumens. For example, check out our lumens placard and tip card. Or listen to some of our radio public service announcements. We have recently launched a billboard campaign effort to raise awareness of lumens in Nashville, Tennessee; Atlanta, Georgia; Phoenix, Arizona; Miami, Florida; Denver, Colorado; St. Louis, Missouri; Detroit, Michigan; and Milwaukee, Wisconsin—so be sure to look out for it if you're driving by those cities.
So, the next time you find yourself looking to replace your traditional incandescent with an energy efficient bulb, choose your next light bulb for the brightness you want and look for lumens—the new way to shop for light.

As for me? After looking for lumens instead of watts, I found an LED bulb for my bathroom that was about 800 lumens. The light quality was great for the bathroom, the color was warm white, and my electricity bill has gone down a lot compared to using the traditional incandescent.

Source: http://energy.gov/energysaver/articles/goodbye-watts-hello-lumens

Lumens in a 40 watt bulb?

Answer:
A lumen is the perceived intensity of the light, as seen by the human eye. The lumen value is largely determined by the the nature of the light, i.e. the sum of the different wavelengths of the light being transmitted by the particular bulb type.

The standard tungsten wire-filament ('incandescent') bulb radiates a different type of light to a flourescent light.
  • a 230 V, 40 watt incandescent bulb produces a light (quality) of about 400-500 lumens,
  • a standard 230 V flourescent lamp of only 7 watts will produce exactly the same value of lumens, i.e. 400-500 lumens.
  • the cool white XLamp XP-G 3.5 V LED lamp of only 3 watts will produce a similar value of lumens, i.e. 350 lumens. And is safer for the workers that make them and better for the environment. It is currently more expensive, but prices have been dropping about 20% per year.
Therefore LED light bulbs convert electricity into light more efficiently than incandescent or florescent light bulbs.
  • For more information, See Related links below this box
Source: http://wiki.answers.com/Q/Lumens_in_a_40_watt_bulb


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