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Watts vs. Lumens and what does it mean to me? February 16, 2011

Posted by bowmanlamps in compact fluorescent.

With new lighting regulations going into effect in 2012, the FTC is doing their part to help educate consumers by developing packaging standards for lighting manufacturers. Currently, consumers use watts to figure out what type of light bulb that they need to purchase. However, with new technologies coming onto the marketplace every day that consume less power, this unit of measurement is not really an accurate depiction of how much light a bulb is going to put out. Having terminology such as “60 watt equivalent” is helpful, but confusing at the same time because a consumer isn’t aware of the energy savings that they are getting from that light bulb. The new standards from the FTC will focus on lumens and not watts to help consumers determine what type of bulb they need to purchase. But, the big question is the difference between a watt and a lumen.

Let’s first start with the definition of a watt. A watt is defined as the power needed to move a one kilogram object at the speed of one meter per-second against a force of one newton. More simply put a watt a measurement of how much electrical power a device consumes. When looking at lighting and watts, you are not looking at how much light a bulb puts out when looking at watts, but how much energy a bulb uses to put out that amount of light.

Now moving on to lumens, a lumen is a measurement of the amount of light that is contained in a certain area. The technical definition of a lumen is one candela multiplied by one steradian. A much simpler definition of a lumen would be that one lumen is equivalent to the amount of light put out by one birthday candle when you are standing one foot away from it. If a light bulb puts out 100 lumens, imagine standing one foot away from a cake with one hundred birthday candles on it.

Lumens are more accurate way of measuring the amount of light a particular bulb is putting out, because lumens are a direct measurement of light output. Wattage, even though it is what people have become accustomed to seeing on packaging and measuring how much light they are seeing, it is not really an accurate way to measure light output. Just because a light bulb uses a particular amount of energy to run, does not mean that it directly correlates with the amount of light that is put out. With a variety of energy efficient CFLs, LEDs and Halogen lamps coming onto the market on a regular basis that do not use nearly the same amount of energy as incandescent bulbs it makes sense for people to move away from thinking about wattage when they purchase a bulb and start thinking about lumens.

This article first appeared on BrightPoint, the TCP Blog.



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