autoflower LED growIn Nature cannabis plants absorb natural sunlight and produce dense and really resinous colas. These big buds are usually tastier, stronger and more potent because inside growers can’t completely reproduce the SUN’s light Intensity and full spectrum. There are various light sources available to growers but not one of them can completely reproduce the full spectrum that the sunlight gives off! Because these grow lights can’t reproduce the full spectrum completely your cannabis plants are receiving less energy than they would under the sun so they are growing slower and can’t be as big as the ones grown outdoors or in greenhouses. This light absorption mostly happens at the ends of the color spectrum at the blue and red colors. Just the opposite happens in the middle of the visible light spectrum and ganja plants receive no energy at all from the green spectrum light as the plant is green and it reflects all of the green light! If you are growing autoflowers with regular light sources (like CFL, HPS, T5 or MH) then you are wasting a lot of energy because these lights produce light curve that is not evenly spaced and with some spectrum spikes that may not be in the right place where your plant needs them. The ends of the light spectrum (Blue, Red) are not in the middle of the curve or in any of the spikes so they get low amounts of light. Imagine if these light sources could give off only the light that cannabis plants need! If this was true then growers all over the world would not be spending money on light that illuminate the room in color spectrum that is not completely efficient to cannabis plants! Here comes in the LED lights as LED diodes can be made with different kind of additives that will illuminate photons in different light colors and spectrum.

What are LED lights?

LED stands for Light Emitting Diode and that means that this light source is just a semiconductor that can perform electroluminescence or in simpler words shine! This “shining” happens when electrons in the diode are pushed into gaps that let them get exited to a higher energy stage and when the electrons return to the starting stage the excess charge is given off as light in the form of photons! These LED light has no moving or fragile parts so there is no wearing out or burning, discharging of a filament as in HID or CFL lights!

LED efficiency & costs

Other lamps like HID and MH, CFL are producing light by a heated filament or gas discharge that gives up photons and usually the light source(filament) is small so the light source is slowly disappearing and it can’t last more than couple hundred or thousand hours. This is why bigger lamps are more efficient but they consume large amounts of electricity and if a grower wants more efficient light he needs to create a massive grow operation because as the bulb gets bigger it increases in efficiency!

For small and medium growers this poses a risk because they are limited in the light bulb efficiency to small CFL and small High intensity discharge lamps that are not so efficient. But there is another light source and this is the LED light! Led’s don’t need to increase in size to be more efficient so small semiconductor LED lights could grow autoflowers with the efficiency of large thousand watt HID lamps.

LED Intensity & spread

LED light intensity is not directly related to the current that is applied but instead the intensity and output is measured in lumens and with different kind of material there can be different intensity and output from the same voltage. On the market there are various grow lights for cannabis plants and their lumen to watt ratio is from 50 to 150 l/watt and those 150 l/watt are right there at the 600 or 1000 W HPS lamp scale in their efficiency. A typical led grow diode runs at 1 or 2 Watts of electricity and they are usually concentrated in a single block like a circular or square box. This alignment gives these combined LED lights the wanted intensity and spread so you can grow premium weed!

You can also buy single LED diodes and combine the needed color spectrum by hand but this setup will be time consuming to build and you will be faced with problems like cooling and connecting these lights. But if you succeed then you can build your set-up on any intensity and spread you want by increasing the intensity and decreasing the spread combining the LED diodes close together or putting them with intervals to increase the spread and decrease the intensity!

LED grow light manufacturers have created various set ups for optimum spread and optimum intensity but you need to examine your grow area and think about what you want from you LED lights.

LED sizes & shapes

Regular LED setups are from 30 to couple hundred Watts and they can be very creative in their shapes. You can get square shapes, circles, lines, patterns and even LED diodes placed in bulb shape. Typical LED diodes used for autoflowering cannabis growing are the ones that are placed in squares, rectangles or circles because they get the most intensity in one space and the lights overall size is smaller.

The sizes and shapes are directly linked with led count and costs so a smaller array will cost less than a big one and for this reason growers sometimes choose to buy multiple LED arrays for Optimum light spread and growth! Getting light from multiple sides is the best deal but making these smaller arrays is pricier and you will get more out of your money by buying larger panel so consider these two things before buying your next LED grow light for your automatic or regular plants!

LED Lifespan

As I mentioned before LED lights have no moving parts and no fragile filaments or glass shells that could be easily damaged. Light emitting diodes are basically 3 layers of materials that excite electrons that are given to them by applying current. This process is very efficient and in theory it can run for tens and even hundreds of thousands of hours and the life expectancy of LED grow lights is given simply by testing those lights under extreme voltages or extreme temperatures. The odd thing is that the rated hour rate is not the burnout time but the time when LED light could be working just with 70 % of the start intensity. But that is not tested completely as well because these times are tens and even hundreds of thousands of hours long. To test these bulbs properly they would need to run for 5, 10 and even more years and there are small amount of grow light companies that have been creating LED diodes for that long! Because of these large numbers LED manufacturers usually give from 20000 to 100000 and even more hours of expected life span of the lighting system but it will almost always run longer than that! In fact there are LED lights from the 70’ and 80’ still running in a non stop lighting rigs! The only danger to LED lights is not the time but the stress of some sort, like an abnormal voltage spike or extreme heat or cold that could damage the layers that produce light. Commercial LED grow lights usually break from the extreme heat if the ventilation is broken or from the voltage spikes that could fuse the diode.

This is good for autoflower growers as in theory you should be able to run these LED bulbs continuously for decades and get amazing energy savings, but in reality you will need to change the cooling systems and sometimes these lights can be fused. If the circuits with these diodes is made properly and the cooling part can be easily changed then you will be able to grow your automatic crops many times over and save money as more and more time passes and your initial investment pays off!

LED Color Spectrum and PAR

LED grow light are small and efficient in their energy to light conversion but they have another advantage and that is the possibility of giving plants only the needed color spectrums of the light. Basically light is just a wave and if the size (frequency) of that wave increases or decreases we see those as different colors! If an object has a structures that can absorb light in a special wavelength it will only take in those photons that are of that exact wavelength. In cannabis the protosintetically active parts are the chloroplasts that have molecules in them called photo pigments that each have a special structure to absorb photons only from one wavelength. These photo pigments are scattered around the plant and they usually absorb broad spectrum of visible light except the wavelength 510 nano meter or as we know it – Green light! The most amount of photo pigments are of the 650 and 475 nano meter scale or the RED and BLUE light so a light source with light mainly in these wavelengths would grow the best autoflower cannabis plants! But don’t think that autoflowers need light only in these colors because they absorb it the most. These plants need light from all the visible spectrum and the more the better! Here again comes in the LED light that can produce light at a specific spectrum and by doing it trigger the right kind of photo pigments that can be found in the greatest amounts.

The coefficient that represent the value of light that plants absorb in the light source is called PAR of photo synthetically active radiation and the best PAR is in the LED grow light sources!

LED Price

Led lights can be bought for as little as a few bucks and can be as pricey as at lest a thousand dollars. In the average grow light there are from ten to thousands of light emitting diodes and that is why LED light are still pretty expensive! Led lights need to be made with strict precision and with different kind of materials to get the desired light spectrum. LED’s are produced by slowly building up layers of material on a sapphire, gallium arsenide or other material beds layer by layer. These materials need to be applied in a very precise pressure and with no impurities and that is why this process is not cheap. As the LED industry increases and the companies making these diodes get bigger they will be able to lower costs increasing the volumes of lights created and we will be seeing a lot of price decline for LED lights in the future.

But for now the average grow light costs more than a CFL equivalent or HPS / MH equivalent but as we know they are more efficient for plant use and last longer so ultimately they are way more economical and you just need to invest more money up front.

You can find many LED fixtures that do 3 to 4 times better that HID or CFL lights and because they last that long it is a bargain!


The main disadvantage to these LED lights is the upfront cost and even if growers know that they will save money in the long run they are hesitant to invest so much money in the beginning!

Another disadvantage could be the light that is coming out of these LED fixtures as it is not full spectrum and it is not glowing in white/yellow glow but can be illuminating purple or violet light. Under this light plants look like they are in different colors but for some growers these colors are more acceptable and even an art form as your plants look more exotic and fun!

The final disadvantage could be the misinformation of LED grow lights by growers and salesman wanting to exploit them by building up LED fixtures that are nowhere near the ideal light spectrum distribution. These grow lights are usually very cheap and the producers don’t give off the data on what nano meter diodes they have and just say bloom or vegging lights, so watch out from cheap ripoff LED lights from unknown companies. Good companies can produce LED light cheaply as well so don’t be reluctant to think that only pricey lights are good and ask fellow growers what the best light fixtures are and how they produce. I will recommend some good LED fixtures. But if you want to know more about any other light source you can ask me in the comment and email or ask around on cannabis forums where someone will be willing to answer questions!


  1.!I have.a.120W.led.Panel.tha a.friend.of.mine.have.made!we.have.copy.the.original led.pannel.product(1Watt=1Led)!SO! under the.homemade.led.pannel;

    • Hey tnx for stopping by and good luck with your grow !
      As for How much plants, that depends on the strain and methods of growing, if you use LST then I think you can train two plants to cover the whole area, but if no LST is used then I think you can manage 4 small plants.

      • I have a 400 watt bulb and balast that i have used to ok i also own a led BL001 FULL SPECTRUM SQUARE it has blue and red from what i starting autoflowers and realy need to get advice on keeping the bulb and balast or swapping to my led asap…input ac85 265v 50/60hz..output dc25 48v. 240MA constant current..first time auto and want to reduce jeat and fan noise in bedroom..small 2 plant grows so want to know if led is big enough to swap to as i also have a small bulb i can add to the side.i was given leds and never used them and dont want to ask friends as anymore than 2 people knowing its not secret..please jelp

  2. Have been using 400w HPS/MH Sun system in a 4’x4′ closet. What would you recommend (LED) to replace this? One large or two smaller lights? Brand names and approximate costs would be appreciated. Thanks CEP.

    • I think two smaller ones are better because they illuminate wider area and the light originates from two points so you will have greater growth. As for the brands I have 4 lights that I recommend on the post, but in general I like the UFO light fixtures. I am working on a LED light comparison chart so if you are interested you can subscribe to my newsletter and when it is ready I will email it to you.

  3. Thanks.a.lot!i.also.subcrise.with.,!I.will.use.soil(,mix.from.biobazz);(i.know.that i.should.left.this.commentat.nutrients.comment);

    • Thanks for subscribing!
      As for the brand, I usually don’t get to attached to one brand, but I much rather look at the the N-P-K numbers and what secondary nutrients are in the mix. I have grown with many different nutrients and even with some cheap cactus mix as it had a lot on nitrogen.

    • Hi there, how many plant do you intend to grow? if one plant in that box then I think that 100 W LED light would be enough and maybe even too much!

      • officinalis on

        I was thinking of SCROGing as much of the area as possible. Not sure how many plants that will take.

        • If you ScrOG them then you can definitely get something in that 100W range as you will be able to get that plant canopy at the right distance from the light to maximize the growth!

    • Hi, tnx!
      Have not seen them around, are they any good, and what are they’r advantages?

      • I recently picked up their full spectrum light. They have lots of ‘sciency’ statements behind their claims. They were pricey and I would have bought others had I known about hem but I’m an LED newb 🙂 I’ll post my opinion after my first grow, but if you get a chance check out their site. I’ve seen posts on some forums backing their claims, and others denouncing them so I’d be curious what you think.

        Cheers, and thanks for your hard work here!

        • I checked up on them and if their claims are true that they’re lights are 2x better than T5 fixtures then it would be amazing.
          I am curious how will your grow go and if they will perform as good as they state, but from the looks of it their products seem legit.

  4. Yanksfanelite on

    I am also new to the LED world and just bought a 90 watt tri-band ufo that I plan to use in conjunction with two 60 watt 3200k cfls for growing two blue mystic autoflowers at a time. In your opinion, do you think that I can be successful with this light setup for 2 autoflowers? I have been extremely successful with my 250 watt MH/HPS setup I have in another location but starting another location with the LEDs. Thanks ahead of time for any help!!

    • I think you most certainly can suceed with that amount of light if that LED has the right spectrum light output then it will be as powerful ar that HID system.

  5. Great site. Subscribed to the newsletter.

    I got here from that awesome auto-grow guide. I’m going to do a grow inside of a big trash can, so I think LED”s are the best way to go (which is how I landed on this page). Perhaps the problem is on my end, but I don’t see your recommendations for LED lights (I just see the title of the section…)

    Can you please give your suggestions again? I’m thinking of using either a 30’ish or a 50’is gallon can. I’d like to grow maybe 4 plants or so. Since this is my first grow, I figure I have a better chance increasing yield with more plants rather than try and push one plant to the 9’s.

    • Hi, You maybe have AdBlock enabled as sometimes it do not show products from Amazon.
      About the plant count, you are completely right – with more plants you will have better redundancy and if something goes wrong with one of them the rest will still be OK.
      I am not an expert in LED light field, but you can check out those TaoTronics UFO grow lights as they are cheap and have great customer ratings.

      • Hi,

        I’m a first time grower, looking to grow between 1-4 auto feminised plants, can you please tell me if the UFO Tao Tronics would be suitable for this…? I’ve read so many articles and such that I think I’m going to go crazy. Many Thanks for any info I may receive.

        • I’ve read somewhere that these types of lights will cause hermaphrodite? (Male and female characteristics) to auto flower plants…? But I really know nothing so please forgive my naive questions. Thank you all…!

          • Hi Dave,
            In My opinion Tao Tronics UFO grow lights are great for autoflower growing and I have not seen any abnormal hermaphrodite production when growing under LED UFO lights. They consume low wattage and are quite powerful!

  6. I bought a veg and separate flowering LED grow light called Dirt Genius and am, so far, very pleased with them. In 21 days from seed my autos are about 8 inches tall and very bushy. The lights were about $125 each, but I did buy the smallest ones they had, since my grow area is only about 4 square feet. Can you find out anything about these lights? Their quality appears excellent. I’ll include links from my seller, though they are also available on Amazon at a slightly higher price, from the same vendor, with free shipping either way. With these links first time purchasers can save $10.

    I came onto your site because i was looking for info on when to change from the veg light to the flowering light with autoflowers. Any help you have would be appreciated.

    One more note: the veg light ran a bit hot from the vents for the first 5 or so days, but has cooled down and is running 24/7.

    • Hi csmile,
      I have not used those lights so I feel I am not competent to discuss their performance.
      But looking at the features in those links looks like a bargain to me.
      As for the change from vegetative to flowering – You should do that when the first pre-flowers appear but you can also run both lights simultaneously for a while to increase the growth in that early pre-flowering phase.

  7. llllll|llllll|llllll on

    Im currently running a 300W (100x3W) Hydro-HollandStar

    Red light 660nm/630nm band [flower band]
    Blu-ray 460nm/450nm band [leaf growth]
    Infrared 730nm/850nm band [promotes thickening of the stems and leaves, effectively avoids the leggy growth]
    UV 380nm/410nm

    What is the “UV380nm/410nm” band needed for???

  8. I have made abox 600x600x1200i , using 135w triple spectrum led, what sort of distance should I have the light away? I have 2 walls lined with mylar, the other 2 are white

  9. TwoDOG125 on

    Let me first thank every one for the info provided here in. In 2009 my health took a dive the Dr. sent me home with these words” you need to have your shit in order there is nothing more we can do for you” I was down to 87 pounds and had to be carried where ever I went I felt the hand of death had me and would not let go till I was his. A wayward friend told me that a lot of my problems might be relieved if I smoked I became angry with him and he said to me the same words I used on him years early ” If your not going try something different WELL FUCK YA THEN SUFFER NICE TO HAVE KNOWN YA ASSHOLE’ he lay a blunt on my night stand and walked out and walked out with out another word. , it lay there three days I relented , within thee weeks I was able to sit up on my own another month I regained my healthy self and started to grow my own well aware of the law, I AM ALIVE AND DO NOT SUFFER MY CONDITION PRESISTS BUT WELL WITHIN TOARENCE FAIR TRADE IF THEY COME TO GET ME. I am a med. pat so it is important to me to know what is in my meds, I first started CFL, home made, then commercial ( 2000 watts ) Vedge astounding,, flower not so much. Light harvests . This is in no way a product indorsement how ever, After much research I contacted California Light works, they were vary cordial as well as understanding ( I’m a nitwit with the tec) I chose their Solar storm 440. Amazed is an understatement , the 440 has both vedge and flower mode as well as T8 UVB. Growing the same strain same number of plants head to head, Simply stated, CFL final tally 4 1/8th oz Solar Storm 440 10 1/16th oz. The 440 is equal to 600 watts MH, and I feel the T8 UVB increases tryk production ( A noticeable diff) I was concerned over the coast , NO longer I now only have to grow one cycle to have enough meds on hand instead of a constant grow going ( worth the paranoia relief alone as I only risk my ass a grand total of 12 1/2 weeks out of a year ) I truly wish I had started using the440 from the jump. I hope this will give at least one person a place to start, then it will have been worth sticking my head up. keep up the work your info has and is invaluable to me as I hope many others. THANK YOU ALL, Two Dog125

  10. Hi great info on this site I’m on my first auto grow using 2 mars hydro reflector 48s I believe these give me somewhere round 300w hps equivelance according to mars hydro website. I have a mixed grow of 4 different plants in an 80x80x160 tent. Do you think this is sufficient light? I can add more if necessary but don’t want to add unneeded light.

    • Hi Bobus,

      I haven’t used those specific LED’s myself so I can’t accurately judge how much power do they produce. But if you say that they give out about 300W of light then it would be best to get some additional lighting to have at least 100W-150W per plant.

  11. hello. great post I am as well as new grower and I want ed to know your recommendation for a tent 48x24x60. Ill be growing autoflower. thank you for your help

  12. greg briggs on

    hello greg here , my question is for optomle growth under led with grow tent 1200×2400×2000 with auto bloms what would be the best size led to use ??

  13. Max Power on

    Bought mine off Amazon, selected the highest rated. Purchased one 1,000 watt and two 300 watt for a 2 X 4 tent. Sunglasses are a must when working with the plants. I’m happy with production. First auto grow. Later I’ll post harvest weigh.


  14. You have a vague grip on the subject of lighting. Lumens are for humans not plants. Lumen output is light intensity that the human eye can perceive not the energy that a plant can absorb. PAR is the light spectrum a plant uses, its not a measure of anything. You need to focus on the PPFD per square meter per second and the daily light intergral DLI. Look it up and graduate to the next level

  15. Cody haupt on

    I bought some cheap grow lights and I am three days into the process after a 24 hr germination my light has a white (full spectrum) setting and a red and blue setting should I start the seedling on red and blue and then go to full spectrum or what setting should I put it on ? Please help I have it on red and blue as of now .

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