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Conversion lumens to watts

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  • Conversion lumens to watts

    what is the conversion of led lumens to watts?

  • #2
    Re: Conversion lumens to watts

    Originally posted by Unregistered View Post
    what is the conversion of led lumens to watts?
    There is no simple conversion. There are two issues:
    *The lumen estimates optical power as perceived by a human observer (plants are hugely different, and other species of animals are probably different). The human eye response varies drastically with wavelength or frequency. At a wavelength of about 555 nm (exactly 540 THz), 1 lumen = 1/683 W. At any other frequency, considerable more power is required for a perceived lumen (orders of magnitude, when well off 555 nm.). The actual optical watts at each frequency have to be weighted by that curve and integrated over frequency to get total lumens. For a fairly monochromatic LED, just use the curve.
    *Any light source is inefficent, radiating only part of the power used as light at the intended frequency. The rest is wasted as heat.

    The curve of nominal human eye response can be found by Googling CIE standard observer.

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    • #3
      Re: Conversion lumens to watts

      This is a well written piece on the "technicality" of the issue, but leaves a bit to be desired for the average homeowner. Based on several searches trying to find a reasonable "conversion guide," here are the number of watts and the lumen equivalent: 40W = 450 lumens, 60W = 800 lumens, 75W = 1100 lumens, 100W = 1600 lumens, and 150W = 2600 lumens.

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      • #4
        Re: Conversion lumens to watts

        So these new LED replacement bulbs that are under 100 lumens are pretty worthless around the house! and the cost $50 each

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        • #5
          Re: Conversion lumens to watts

          Well, the "official "candle is ~ 12 lumens , so it would take ~ 37 candles to match a 40W bulb? That seems like a lot.

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          • #6
            Re: Conversion lumens to watts

            Officially, since the LED luminous efficacy and lifetime is high and long, they're supposed to be worth more upfront when you account for the total cost of ownership.

            The emitted spectrum is displeasing for some, though.

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            • #7
              Re: Conversion lumens to watts

              Unregistered stated:
              "here are the number of watts and the lumen equivalent: 40W = 450 lumens, 60W = 800 lumens, 75W = 1100 lumens, 100W = 1600 lumens, and 150W = 2600 lumens. "

              These figures are for traditional incandesent bulbs NOT leds. LED lumen output varies per watt varies between manufactures and designs. But a 5 watt LED "bulbs" are usually designed to replace 40W incandesent bulbs (450 lumens) and 7 Watt Led "bulbs" replace 60W incandesent (800 lumens). LED downlights are often a little more efficient with 3 watt sometimes claiming to producing as much light as a 50W halogen. However, downlights do not have the same ambient effect in the room so often do not look as bright to the human eye.

              I am designing my LED lighting withe downlights assuming that a 3 watt LED down light is the equivelent of a 20W incandesent.

              I think you can pretty safely assume from the information out there that 1W LED (with quality ultra-bright LEDs ) equals about 100 lumens output for most standard lighting solutions, eg not strip lighting or flood lighting

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              • #8
                Re: Conversion lumens to watts

                Actually just looking through my shoppling list now and it seem retailers information across a range of products puts Lumen output of most LEDs at about 60 lumens per watt.

                This would make a 13 watt LED the equivatelent of a 60 Watt incandesent (800 lumens). But I personally find them better than that, base on my experience withe bulb replacement varieties. But I can be a bit light sensitive.

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                • #9
                  Re: Conversion lumens to watts

                  Actually like another poster suggested, Lumens are dependent on quality of chip and how the bulb is built. We manufacture our own LED bulbs for sale in US. We has some chips we use give out only 60 lumens/watt while some others give out 120 lumens per watt.

                  Also its worth nothing that besides counting lumens, you also need to pay attention to watts consumed. This is where Lumens efficiency comes into play. for more info, go to mygreenpros.com and get idea on what we sell

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