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Discussion in 'Home Power and Microgeneration' started by JoeSP, Dec 11, 2005.

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  1. JoeSP

    JoeSP Guest

    I have seen in articles that white LED lights use less power than regular
    lightbulbs. Nearly always, they say something like "much more efficient
    than incandescent." But when you look up the specs, they usually work out
    to 12-20 lumens per watt. That's not better than incandescents at all.
    What gives?
     
  2. All lights are not created equal. The incandescent bulbs used in
    flashlights are many times less efficient than 60W (and up) bulbs.
    This means that you can replace a flashlight bulb with a white LED
    and it'll run off the batteries a lot longer. You can't replace a
    60W incandescent room light or 100W halogen fixture with LED and
    expect to save any energy.

    Single color LED is much more efficient than white versions so for
    places that you would use an incandescent with a color filter (turn
    signals, brake lights, stop lights, etc.) you'll save lots using
    LEDs.

    Anthony
     
  3. m Ransley

    m Ransley Guest

    White leds were apx 18 lpw max a year ago , now I hear 70 Lpw are out
    and 110 Lpw designs are working. I think alot of sales is lies, but soon
    people will benefit from efficient Leds, but at what price. Now T8 tube
    is best for home use. In the future who knows.
     
  4. Steve Spence

    Steve Spence Guest

    You just uncovered marketing's dirty laundry. More efficient for task
    lighting, not more "electrically" efficient. For reading a book, an
    incandescent is overkill, the wrong tool for the job. LED's are
    directional, perfect for putting a small amount of light right where
    it's needed.
     
  5. JoeSP

    JoeSP Guest

    The only reason an LED lasts longer in a flashlight than an incandescent
    bulb, is because as the incandescent bulb dims, resistance in the filament
    becomes less and less, speeding up the battery discharge. An LED bulb will
    stay lit much longer as the battery dies, albeit at a lower light output.
    It also remains the same white color, not a reddish yellow as the battery
    dies out.
     
  6. Plus longevity of the bulb - one reason why everybody is using LEDs for
    traffic signals these days.

    My LED flashlights definitely don't get the power output that my big
    incandescent lantern does, but I only replace the batteries (2 D cells)
    twice a year as opposed to every month (the big square 6V battery).
     
  7. Dave

    Dave Guest

    Another issue is that standard 5mm LED's, while they may 'go' for 100,000
    hours, their light output degrades quite quickly- in the order of 30% after
    9000 hours and this degradation continues past this time frame. Google
    'LED degradation' for some 7,000,000 pages!

    OzDave
    www.rpc.com.au
     
  8. Steve Spence

    Steve Spence Guest

    I installed LED nightlights throughout the house. The battery pack
    barely knows they are there.
     
  9. JoeSP

    JoeSP Guest

    Your point being? Low lumens per watt mean less than your own opinion that
    they are very efficient?
     
  10. Vaughn

    Vaughn Guest

    And your point is?
    The only thing that I can think of in that size, and for that use (night
    light) that would be more efficient than LEDs might be small neons or perhaps
    cold cathode, but both of those take an inconvenient voltage.

    Vaughn
     
  11. Lumens per watt is lighting effeciency.....are you saying LEDS are not
    effecient?
     
  12. Yeah, we have one of those - something like 0.04W, iirc.
     
  13. The point that both Steve and I made is that you choose your lights with the
    purpose in mind. If all you want is a nightlight, you want simply the
    lowest possible wattage - because maximum lumens is not only
    inconsequential, some studies have shown that even the light output from an
    incandescent night light can be detrimental to your health. If you want a
    reading lamp, small CFs are perfect. If you want to light the bathroom
    mirror, wattage becomes almost pointless - it doesn't matter how much power
    you've saved if your wife says it makes her skin look green!
     
  14. JoeSP

    JoeSP Guest

    Of course I'm saying that about white LEDs. Haven't you ever looked up the
    specs? Or are you content to believe the myth that they are all equally
    efficient and use almost no power?
     
  15. Steve Spence

    Steve Spence Guest

    My point is that they use less electricity than a standard nightlight,
    and I'm saving watts. incandescents are less appropriate for that
    particular usage, LEDS are more so.
     
  16. Steve Spence

    Steve Spence Guest

    of course, but they are appropriate in certain task lighting (and
    instrumentation) situations due to their minuscule power draw (and
    corresponding minuscule lumen output). LED's have similar efficiency
    (lumens per watt) to incandescents.
     
  17. Steve Spence

    Steve Spence Guest

    Not even measurable on my KAW.

    But enough light to find and use the toilet at night.
     
  18. JoeSP

    JoeSP Guest

    I see. So when the power draw is small, it's the same thing as being more
    efficient.
    Anything is better than being proven wrong.
     
  19. Steve Spence

    Steve Spence Guest

    Bingo!
     
  20. JoeSP

    JoeSP Guest

    But did you consider that the reason they use less than an incandescent is
    because they put out less light? You just can't get away from the fact that
    white LEDs aren't more efficient than incandescents. Your constant attempts
    on the "last word" on everything doesn't make you right, it just reveals
    how little you actually know before you profess great knowledge on the
    subject.
     
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