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I am building an led light for my indoor hydroponic / aeroponic / foggaponic hybrid herb garden. I am currently using a 100W warm white LED module. It works fine but I am also building another RGB light and that got me thinking that since plants do not use green light I am wasting 33% of the light / electricity.

I would like to get a comparison between different light spectra and the efficiency that I can gain / loose by using different lights. Since white (normal or warm) LED modules are significantly cheaper than special grow lights with multiple spectra I would calculate whether it is worth paying an x amount more for non white modules or not.

Here are the lights I am considering ( assume they all have 100W output for simplicity ):

White - 6000~6500K color temperature Warm white - 6000~7000K color temperature Red + blue only

Finally I could use an RGB LED and customize the color to anything I wanted even changing during the day / season. Would this option be of any benefit compared to reg+blue only? I would generally want to keep my plants in vegetative stage so changing spectrum to force flowering is not really useful for me, this leaves only plant efficiency when it comes to different light spectra.

  • I added an answer, but will wait another week or so to see if someone can post a better one before I accept my own answer. – DominicM Mar 29 '14 at 14:34
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Dominic, This discussion LED spectra(and links from the paper) should be right on the money - also the linked paper has some useful info on green light use by young growing plants

  • It looked promising but unfortunately the answer is too vague and even incorrect in one part. – DominicM Mar 26 '14 at 20:50
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I found Surexi Spectra Guide document. It has very useful info on what light is required for what stage of plant growth. It's not ideal since it's not an independent organisation but a company that makes LED lights. Still, the spectra used in commercial led lights should certainly be a good starting point for building my lights.

Here's a summary of the document - red:blue (ratio):

5.4 : 1 (+ ~0.2 green & yellow) - Germination of seeds requiring light to germinate, flowering plants.

3.5 : 5 - Vegetative plants.

1.5 : 6.5 - Seedlings.

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