Growing plants with LED grow lights is currently one of the hottest topics in indoor gardening. Gardening with LEDs is fairly new and only done by a handful of gardeners so there are many questions surrounding them that the indoor garden community wants to know. Do LED’s really save electricity compared to an HID? Is the high cost of an LED made up in electrical savings? Can you successfully flower summer crops under an LED grow light? Personally I’m very interested in the idea of using LEDs for growing plants. Reducing power consumption is great for society and even better for my wallet. But when looking online to answer these questions I see a lot of LED manufacturers or retailers hyping the amazing advantages to LEDs. Like the saying goes, “If it sounds too good to be true it probably is” so I decided to do some research on my own. Let’s see what we can find out.
Growing summer crops indoors under artificial plant lights is expensive. You’re essentially trying to replicate the sun’s intensity during the June, July, and August months, indoors. Until LEDs came to the retail garden market the only way to reproduce that intense light was with a power hungry HPS or MH light. So saving energy has always been of interest to anyone using a grow light. When electronic ballasts first entered the market about 8 years ago they were able to produce more light while using the same wattage as the magnetic ballasts which dominated the grow ballast market at the time. Light output, and therefore growth and overall yield, increased anywhere from 10-30% when using the new electronic (digital) ballast. Nowadays, electronic ballasts have taken over the grow ballast market while magnetic ballasts collect dust on the shelves. So it begs to question, if an LED that uses 650 watts can produce as well as a 1000 watt HPS, as many LED manufacturers claim, why aren’t they taking over the grow light market the way digital ballasts did 8 years ago? Why aren’t they the light of choice for most indoor gardeners?
Personally, I’ve have good success starting seeds and rooting cuttings under a 45 watt LED panel that utilized simple low wattage blue and red diodes. I’ve also grown young plants up to about 10” in height under the same 45w panels. Growth was always adequate and comparable to that of a T5 fluorescent. But my own experience with LEDs was limited and I’ve never used a high powered LED grow light so I needed to find another grower who had actually done some full cycles using an LED light.
I looked up my old friend Doc because I remembered he had been doing some tests with LED Grow Lights. I interviewed Doc because I knew he would give me honest feedback and he was a very experienced gardener. Like myself, Doc was very interested in the concept of using LED grow lights and was hoping for the best when conducting his tests. In the last 12 months he said he was able to do 3 separate tests using LED Grow Lights. Here are his findings.
Test 1
Materials:
LED total power consumption: 650 watts
Diodes: Red, blue, and white 3 watt diodes
Media: Organic potting soil in 3 gallon plastic pots. Drip system.
Nutrient: Popular 100% organic nutrient
Grow area size: 3’10” x 3’10”
In the first test Doc used an LED grow light that used 3 watt diodes and approximately 650 watts of total power. He also used 3 gallon buckets of quality potting soil with a drip system and a premium 100% organic nutrient.
Results: This test was never finished. There was a problem with the soil not drying out fast enough between feedings which Doc believes led to weak growth. Possible complications may have been the lack of heat from the LED light. This was something very new for Doc who like most indoor gardeners have only grown with T5 fluorescent and MH or HPS grow lights. Doc noticed how much his grow room relied upon the heat from his HPS lamps to bring his room up to optimal temperatures. During the test his grow room stayed around 60-65 degrees when his lights were on. Not only is this too cold for proper fruiting and flowering of most summer crops but it also didn’t allow his potting soil to dry out fast enough leaving his root systems water logged and starving for oxygen. About 2 months into the grow Doc decided to start over.
Conclusion: Inconclusive.
Test 2
Materials:
LED total power consumption: 650 watts
Diodes: Red, blue, and white 3 watt diodes
Media/Water: Hydroton in 1 gallon fabric pots. Ebb and flow.
Nutrient: Popular 2-part hydroponic nutrient
Grow area size: 3’10” x 3’10”
Using the same 650 watt LED grow light Doc switched from soil to hydroponics to have more control over the watering. He used 1 gallon fabric pots with hydroton grow rocks in an ebb and flow hydroponic system. He also added heat to bring the temperatures to a more comfortable 75-80 degrees when the lights were on.
Results: This test run was much better than the first and strengthened his theory that lack of heat was the main culprit his first time around. Health was good and bugs and or disease was non-existent. Keep in mind Doc is an expert grower and expert growers know how to keep a grow room healthy and free from bugs or disease. Yield was not as good as Doc would have hoped. While overall quality was consistent with plants grown under an HID light, Doc’s yield for his 650 watt LED grow light were closer to or slightly better than what you would expect from a 400 HPS light using a full spectrum HID bulb.
Conclusion: Fail. Yields were okay but we didn’t get a better yield to watt ratio than an HID grow light. There was also an extra energy cost to run the supplemental heat.
Test 3
Materials:
LED total power consumption: 650 watts
Diodes: Red, blue, orange, and white 5 watt diodes
Media/Water: Organic potting soil in 3 gallon plastic pots. Drip system.
Nutrient: Popular 100% organic nutrient
Grow area size: 3’10” x 3’10”
For his third test Doc switched lights and decided to use an LED grow light that used 5 watt diodes which are much brighter than the 3 watt diodes. This light also included orange diodes which the previous light did not. He went back to using an organic potting soil in 3 gallon pots and the same 100% organic nutrient he had used in test 1.
Results: The 5 watt diodes gave off more heat than the 3 watt diodes helping to maintain a more comfortable ambient temperature for the plants. Growth and yield came out equal to the growth and yields he would expect from a digital 600w HPS grow light (which actually consumes around 640-650 watts of power per hour). This improvement led Doc to conclude that the higher powered electrode equalled a higher overall yield. Ambient temperatures were about the same as in test 2 since a heater was used in that test to raise temperatures closer to an optimal range. Supplemental heat was not necessary in test 3.
Conclusion: Fail.The goal of these tests was to get a better yield to watt ratio than an HID grow light, a true test of efficiency, and that didn’t happen. I could possibly have given this last test a pass rating. In my opinion, equalling the yield of an HPS light is an impressive feat. But LED manufacturers constantly claim that LEDs are more efficient than an HPS and so I felt obligated to grade them based upon just that.
LED Test Synopsis
Doc’s results were very interesting. What stood out the most was the dramatic increase in yield when he switched from 3 watt diodes to 5 watt diodes. Using the same amount of power Doc was able to increase his yield by about 30-40% using the larger diodes. When comparing his yield per watt using the 650 watt LED with 5 watt diodes to that of the 600 watt HPS digital ballast (which uses 640 watts) he realized about a 1 to 1 ratio. So growth per watt was the same. This leads one to theorize that if an LED grow light were to come out with a diode that was larger than 5 watts, then the overall ratio of yield per watt could begin to turn in favor of the LED grow Light. What is unfortunate is that if you believe the sales pitch given by most manufacturers of LED grow lights then you probably believe that you are going to get a much higher ratio and this just isn’t the case. In other words, at least in our tests, an LED using 650 watts of power does not equal a 1000 watt grow light. From what I’ve read online it seems that Doc’s results were closer to those experienced by independent bloggers.
What Makes a Good LED Light?
As technology improves so will these test results. LEDs are hot. Residential, commercial, automotive, televisions, anything that uses a light source has recognized the energy value of an LED diode. And therefore there is a lot of money being poured into the technology and the gardening industry is no doubt going to benefit from that. So let’s look at a few things that need improved to create the ultimate LED grow light.
Spectrum
One one of the biggest hurdles LED grow lights have had to get over is the limited plant spectrum LED diodes offer compared to an HPS, Metal halide, or fluorescent grow light. HID and fluorescent grow bulbs can be designed to emit a specific spectrum that has been optimized for plant growth, and more specifically, different stages of plant growth. To date, LED lights are unable to combine all colors in the light spectrum in one single diode. Therefore in order to get a blend of colors, LED lights combine different color diodes to produce a specific spectrum that plants will respond to with healthier growth.
Now this is neither good nor bad. It just means the light spectrum that the grow light is producing is produced differently in an LED compared to a full spectrum HPS. It’s important to note the ability that an LED has to manipulate a specific color in the light spectrum to produce the maximum peak spectral output of a specific color in the light spectrum. The most notable color to mention is red which is a prefered color by plants during the blooming stages. Currently, HPS lights do not have the ability to provide the maximum spectral output of red light that a plant can use but an LED can. By maximizing that spectral output, you maximize the amount of light photosynthesized by the plant. Another advantage over HIDs that many higher end LEDs have is the ability to change the light spectrum using a dial or a set of switches. As technology improves I’d expect that the level of light spectrum manipulation will improve as well.
Light Intensity
Another big area of concern for gardeners thinking about growing under LEDs is the amount of light intensity that LED grow lights are able to provide. We saw obvious differences between the 3 watt and 5 watt diode in our tests with the 5 watt diode showing a much better ability to bloom summer crops that are used to the intense sunlight and warmth available during the summer months. While warmth can be artificially added to a grow room, light intensity is usually supplied by a Metal Halide or High Pressure Sodium HID light. Even the best fluorescent grow lights will not grow fruits and flowers as big as an HID (high intensity discharge) light. So for now I have to give HID lights the advantage over LEDs when it comes to light intensity. Not only is this intense light necessary for fruiting and flowering plants to reach maximum growth but also for the ability of the light penetrate deeper into a plant canopy. This means that when growing taller plants, the more intense your light is, the more budding sites you will see growing vertically along the plants stems. And generally more flowering sites means bigger yields.
However it’s not all bad news for LEDs when it comes to intensity. Our final test showed that the current LED technology is capable of growing plants and producing harvests at least equal to that of an HID when comparing yield to watts. We also saw that when the diode size was increased, so was the growth. Therefore, it’s theoretically possible that when, not if, larger diodes are available, growth and yield could increase even more. Of course we don’t know how much more power will get used by these new larger diodes so for now we’ll just have to wait until they become available.
Heat
I wasn’t planning on adding heat as one of my points to talk about but after getting the feedback from our LED tester Doc I chose to include it. Why? Because even an experienced grower like Doc made a point to tell me, “I was really surprised how much I missed the heat that my HID lamps provided”. What this tells me is that LEDs can be a huge advantage to anyone battling heat in their grow room but could cause some problems for anyone growing indoors during cold weather or in cold damp areas like a basement. Moving forward I expect the heat output from an LED to increase as light intensity and diode size increases but once again we will have to wait and see. So depending on what LED light you choose, heat or the lack of will have to be dealt with by the grower to insure maximum plant yield.
The Future
The future is bright for LED lighting. I’m very excited to announce that one company I talked to recently will be coming out with a new LED in the next couple months that uses a higher powered diode than what is currently available! This new LED grow light will also include the ability to choose from 7 or 8 different Kelvin settings so that you can literally dial in the spectrum you want! Would you like to start your plants under a 6500 Kelvin spectrum of light for excellent vegetative growth, switch to 3000 Kelvin for your bloom stage and finish up the last 2 weeks with a 10,000 Kelvin spectrum? Sounds like it’s going to be possible. We will be sure to test this new light when it’s available so look for the follow up article in future newsletters. As soon as it is available to the public we will have it for sale at our eHydroponics online store. Cost is expected to be around $1500 and as always you’ll get the best price on it at eHydroponics.com, guaranteed.
I hope this article helps anyone interested in growing with LED lights. Just writing about it has been fun and exciting. There’s so much possibility when it comes to gardening with LEDs. Personally I believe there will be a day when growing with an LED light will be the norm and HID lights will be seen as archaic and inefficient. But for now I have to conclude that a full spectrum HPS lamp combined with an electronic ballast or supplementing an HID with an LED light is your best bet for the best possible quality and yields. Happy growing!
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