Today you're getting a review of the best LED grow lights that you can currently buy.
You're also going to become an LED grow light expert in less than 5 minutes.
You're going to get a simplified buyer's guide that covers:
- 2 easy-to-use rules you can use to decide how strong of a grow light to get for your setup;
- A step-by-step process to rate any LED light, and;
- Tips to optimize the performance of your light and maximize your yield.
Let's get started with our most recommended LED grow light.
Quickly go to the…
- #1 Horticulture Lighting Group HLG 650R (Best Overall)
- #2 Gavita Pro (Most Reliable and Longest-Lasting)
- #3 Spider Farmer SF (Best Budget Light)
- #4 Scynce Raging Kush (Most Advanced & Best for Vertical Growing)
- #5 ChilLED GrowCraft X6 (Best Thermal Management)
- #6 Amare SolarECLIPSE (Best Build Quality)
- #7 VIPARSPECTRA Reflector Series (Cheapest)
1. Horticulture Lighting Group HLG 650R (Best Overall)
This light is the latest powerhouse grow light in Horticulture Lighting Group's catalog.
The most important upgrades compared to the previous flagship models of HLG are:
- Supplemental light that covers the deep-red and far-red wavelengths;
- Slightly stronger light intensity (went from 1700 to 1770 μmol/s), and;
- More efficient when we look at the umol/j (went from 2.6 to 2.81 umol/j).
This light comes with four full-spectrum white light quantum boards powered by:
- Samsung LM301H full-spectrum white diodes, and;
- LM351H V2 Deep Red 660nm diodes.
When it comes to efficiency and light ‘output'/intensity, these LED diodes are currently the best you can get.
White light blows any ‘blurple' light completely out of the water when it comes to efficiency and light intensity. ‘Blurple' LED grow lights are predominantly blue and red spectrum lights. 90% of budget LED grow lights are ‘blurple' lights.
White light covers the full spectrum of ‘photosynthetically active radiation‘ (PAR) much better than blurple lights. This includes green and yellow wavelengths. While the exact role of these wavelengths in a plant's photosynthesis process remains unclear, it's thought they do have a role.
White light more closely resembles the sun than blurple light. The more closely your light will imitate the wavelengths of light that come from the sun, the higher quality your yield will be.
But recent insights show that your plants could benefit from wavelengths that aren't covered by white light: wavelengths that cover the deep- and far-red spectrum.
The deep- and far-red spectra of light are thought to be needed for the ‘Emerson effect'. The Emerson effect refers to the notion that two photosystems, one that is sensitive to the deep-red spectrum (680 nm) and one that is sensitive to the far-red spectrum (680+ nm), work together to optimize electron transport and photosynthetic rates, especially in the flowering stage of plant's lifecycle.
Well, this light comes with the strongest and most efficient deep red LED diodes: the Samsung LM351H V2 diodes.
Any LED grow light that makes use of Samsung LM301H diodes, and has supplemental LM351H V2 diodes is going to be great for your yield and your electricity bill.
- Cover a wide spectrum of PAR, and;
- Produce more intense light with fewer watts than other types of LED diodes like Epistar and Cree.
While the initial investment in a light with LM301H diodes may seem steep, it will pay itself off big-time after a few successful grows because you will keep the cost of the electricity bill down.
Not only are Samsung LM301H diodes LED diodes currently one of the best LED chips in terms of PAR-coverage and light-intensity, but they're also the best-value-for-money LED diodes that you can get (will keep the cost of electricity down).
The only technology that comes somewhat close in terms of PAR spectrum coverage, light intensity, and PAR/PPFD efficiency, is COB LED (chip-on-board LED).
And although COB technology will result in amazing quality yield as well, you can get the same result with fewer watts (and a lower electricity bill) when using Samsung LM301H diodes.
When it comes to LED grow lights with Samsung LM301H diodes you have a few options. But if want your LED grow light to make use of Samsung LM301H diodes AND want:
- A light that comes from a reliable and reputable company that has its products tested for many years by thousands of growers;
- Great build quality;
- Supplemental light that covers the deep-red and far-red wavelengths;
- Run cool;
- Last longer than 1 year, and;
- 3-year warranty…
the HLG 650R is your best option for any 5×5 grow tent.
Especially the cooling mechanism and proper spread of diodes are two extremely important factors that can make or break an LED grow light.
The passive cooling mechanism of all Horticulture Lighting Group quantum boards is designed very effectively with heatsinks. With most of their models, you probably won't need any active cooling (although it always helps).
Combine this effective cooling with the most power-efficient white-light diodes and the right spread of diodes for improved canopy penetration, and you have the perfect combination of grow light features to get an amazing yield while keeping the electricity bill down.
Next up …
2. Gavita Pro 1700E (Most Reliable and Longest-Lasting)
LED grow lights are evolving at a fast pace.
What was best 2 years ago, is now replaced with a new LED technology.
New technology in LEDs usually means stronger light for less electricity.
Even though a bit older than some other lights on the list, it's still powered by the strongest and most efficient LED diodes: The Samsung LM301B diodes.
While the LM301H diodes are slightly newer, they're practically the same as the LM301B diodes. In terms of light output/intensity and efficiency, these diodes are extremely similar:
- 0.56 μmol/s, 3.10 μmol/J @ 65 mA (LM301H) vs. 38.8 lm, 220 lm/W @ 65 mA (LM301B).
While expressed differently, when you convert the numbers they're almost the same.
Don't get fooled by the marketing tricks. Just because LM301H diodes are newer, it doesn't mean that they're better than LM301B diodes…because they're not.
Although the Gavita Pro 1700E is one of the more expensive LED grow lights …
When you look at the power and quality of this light, you'll quickly understand why it has such a high price tag.
The Gavita Pro 1700E's output is rated at 1700 μmol/s. This is extremely high for an LED grow light. While it isn't the newest light on the list, it's still one of the strongest grow lights on our list.
Not only is it one the strongest lights on the list, when you look at its umol/j we can clearly see it's also one of the most watt-efficient lights that you can get. It has an efficiency of 2.6 umol/j.
But strong and efficient light isn't the only thing the Gavita Pro 1700E has going for it …
Although much better than with ‘blurple' lights, the coverage of the deep-red and far-red spectrum with white light isn't truly optimal.
The Gavita Pro 1700E solves this issue by supplementing the powerful Samsung LM301B diodes with Osram deep-red LED diodes.
This means that this light even resembles the sun more closely than LED lights operating with only ‘white light' LED diodes.
Of course, as you would expect from a premium LED grow light, you also get great build-quality with the Gavita Pro 1700E:
It comes with eight passively cooled LED bars that provide a very even light intensity across the whole canopy and keep the noise down.
You probably won't need any additional cooling with the Gavita Pro 1700E, it's cooling mechanism is extremely effective.
The best part?
Gavita doesn't drive its diodes as hard as other lights on the list. Your diode-lifespan with this light will be significantly higher on average compared to other lights. This means significantly less color shifting and not needing a replacement for many years.
The bottom line:
The Gavita Pro 1700E is currently among the best LED grow lights that you can get. But you have to be prepared to pay its premium price tag.
Next up …
3. Spider Farmer SF (Best Budget Light)
If you want to experience the power of Samsung LM301B diodes, but don't want to spend $800+ on a premium LED grow light from Gavita or HLG …
You'll be happy to know that there are cheaper alternatives.
Our most recommended cheaper alternative if you want the powerful and cost-efficient Samsung LM301B diodes is currently the Spider Farmer SF LED grow light.
While the build quality of the Spider Farmer SF might not be as good as the Gavita or HLG lights …
The light intensity is only slightly worse …
But MUCH better than other budget LED grow lights.
Of course, you can expect a similar efficiency with the Spider Farmer SF compared to the premium lights that come with Samsung LM301B LED diodes. When we look at the advertised umol/j, we can see that the Spider Farmer SF has an advertised efficiency of 2.7 umol/j.
This makes the Spider Farmer SF, theoretically, even more efficient than the Gavita Pro 1700E.
What's even better?
Although the ‘white light' emitted from the LM301B LED diodes covers a much wider spectrum of PAR than the average ‘blurple' light …
White light doesn't cover the deep- and far-red spectra of PAR as much as you would like.
Well, Spider Farmer lights are supplemented with deep red LED diodes and infra-red chips.
This makes the Spider Farmer SF lights cover an almost as wide spectrum of PAR as the Gavita Pro 1700E and the HLG 550 V2 R Spec.
Next up …
4. Scynce LED Raging Kush (Most Advanced and Best for Vertical Growing)
Often the problem with getting a single grow light to cover your growing area during the flowering stage is:
Even canopy penetration.
When you have multiple plants of different sizes the developing buds at the bottoms and sides of your plants usually don't receive light of the same intensity as the ones at the top.
With a single light, it's difficult to cover all angles of your grow area evenly…
But there are a few lights that come with custom-built optics that are designed to spread the light evenly over your canopy, including the lowest parts.
And the Synce LED Raging Kush is the best option when it comes to even canopy penetration.
When you check the PPFD-chart, you'll see that in a 4×4 growing surface area, the average PPFD reading is 1057 from a height of 9 inches.
But the best part:
The minimum PPFD reading at the outskirts of the surface area is around 1000 (at 9 inches). While with some other grow lights on the list, the PPFD drops more than 50% at the outskirts of your growing area, this light stays consistent in literally every part of the surface area. It gives you at least 1000 μmol m(-2)s(-1) in even the furthest outskirts.
But also vertically, these lights deliver extremely consistent light intensity. The patented Conic 120 optic makes it so that the Raging Kush delivers the same light intensity while hanging between 6 and 18 inches over the canopy.
With an efficiency of 2.51 umol/j, it's not the most efficient light on the list, but still highly efficient and significantly more efficient than other types of grow lights like HPS lights.
Like all the other lights on the list, this is a true full-spectrum LED grow light, it comes with the following lights covering the following spectra:
- White light (475 watts between 2700k and 6500k) so you can cover both ‘cool' wavelengths like blue and green and ‘warm' wavelengths like yellow, red and orange, and;
- 175 watts of deep and far-red light covering wavelengths between 660 and 730nm.
But what makes this light special compared to other full-spectrum lights on the list:
It has ‘full power spectrum tuning'.
Let me explain.
You can fully control what specific wavelengths you want to cover with the allocated watts.
If you want to reduce the cool white light covering blue and green wavelengths during the flowering stage, you can simply dial up the warm white light, without reducing the watts! That means even if you only want warm white light during the flowering stage, you get the full 475 watts.
By dialing up or down the various light spectra, you can fully control the dominant light-type at any given time.
Want to support your plants during the vegetative stage and give them thick stems and densely structured branches and leaves? Turn up the ‘cool' white light.
Want the most potent buds with the highest amounts of resin and trichomes? Turn up the ‘warm' white light.
This is currently one of the most advanced LED grow lights that you can get.
But there are more highly noteworthy benefits that come with this light. The biggest one:
You get a 5-year full warranty on this light. This is above the industry average of 3 years.
You also get full wireless control over your light with the Andriod/iOS Theia app. With this app you can control:
- Intensity/dim from zero to max;
- Ramp on time (sunset/sunrise);
- The exact light spectrum of the light.
The bottom line:
If you're a vertical grower or want predominantly white light, but keep full control over the PAR spectrum, this is the light you should get.
- Click to see the most recent price – (LEDGrowLightsDepot)
5. GrowCraft X6 ChilLEDTech (Best Thermal Management)
While the exact LED diodes used in this light aren't disclosed…
When we look at the output and efficiency numbers, we can only conclude that they must be made with the highest quality diodes.
- Efficiency: 2.81 umol/j
- Output: 1647 μmol/s
As you can see the efficiency is as good as lights that are powered by Samsung LM301H diodes, while the output is a bit lower.
While I can't say with certainty, looking at the numbers, there's a big chance Samsung LM301H diodes power these lights.
When you look at the PAR spectrum of light wavelengths covered by this light, you see that all the wavelengths are covered well, just like you would see with other high-quality white lights.
The GrowCraft X6 has especially good coverage of the red and far-red spectra. What this means is that this light will perform exceptionally well in the flowering stage.
This light, as well, comes with Mean Well dimmable LED drivers. It has a dimmable watt-range of 30-600 watts.
The GrowCraft X6 comes with two different options:
- Flowering optimized spectrum, and;
- Vegetative cycle optimized spectrum.
If you have a lot of money to spend, you could get both of them.
However, if you only want to get a single light, I highly recommend getting the flowering optimized version. Looking at PPFD-chart published by ChilLED themselves, this may also be the highest-yielding LED grow-light on the list for a 5’x5′ canopy area. It has the highest PPFD values even towards the edges of the coverage area.
The Growcraft X6 is another option among high-quality lights that all have similar light intensity, efficiency, and coverage of similar wavelengths of light that are best for growing plants like cannabis.
But what makes the Growcraft X6 special compared to the other options is its thermal management. This light runs a bit cooler than the other premium lights on the list. While the stated operating temperature of grow lights isn't always accurate, this light truly doesn't get hotter than the stated maximum operating temperature of 95°F/35°C.
It comes with a 3-year limited warranty, which is about the industry average.
- Click to see the most recent price – (Chilled Grow Lights)
6. Amare SolarECLIPSE (Best Build Quality)
If you're looking to replicate the sun, the Amare SolarECLIPSE will get you very close.
This is a full-spectrum light in the most real sense of the word:
While 90% of LED grow lights are so-called ‘blurple' lights, mainly providing PAR-output in the blue and red spectra, the Amare SolarECLIPSE is providing a very high PAR-output in the FULL spectrum, including the green spectrum!
It has a very balanced ratio of wavelengths, including the far-red spectrum which is needed for the Emerson effect.
It gets even better:
UV-light has been proven to increase THC-percentages in cannabis, and this is one of the few lights that have an UVB-bulb.
This light is a real powerhouse and literally replicates the sun. Don't take my word for it. If you check the PPFD readings, you'll see this light's PPFD values are off the charts. Not only regarding pure output, but also the coverage area. The coverage area of this light is bigger than other same-watt budget lights on the list when using the ‘minimum of PPFD of 510 μmol m(-2)s(-1) for the full coverage area' rule.
When looking at the actual power draw of this light, you'll see this light has a very high PPFD output per watt (PPFD/WATTS).
Here's how they achieved this:
The LED chips used in this light are based on COB technology (chip on board). COB LEDs are more powerful and efficient, last longer than regular LED diodes, have a more balanced spectrum of wavelengths, and are much easier on the eyes than specific color LED chips.
The main downside of COB is that they're a single-point light source and the spread isn't the best, but Amare counteracted this by providing supplemental CREE chips.
Here's the exact composition of this light:
- 6x CXB-3070's, and;
- 60x CREE XP-G3 & XP-E2 Monos.
The Amare SolarECLIPSE has the best build quality on the list. The cooling is really on point, you won't need any additional cooling with this light. plus you get a 5-year warranty in case anything goes wrong. 5-years of warranty is above-average in the LED industry (the average is 2-3 years), shows you how much they trust their lights.
What's the bottom line?
If you value build-quality over results a bit more …
The Amare SolarECLIPSE is the light you should get.
- Click to see the most recent price – (LEDGrowLightsDepot)
Last on our list is the…
7. VIPARSPECTRA Reflector Series (Cheapest)
The VIPARSPECTRA Reflector is similar to the MarsHydro Mars Pro II Epistar light. It’s a Chinese budget light that provides excellent value for its price.
The quantity and quality of your yield with these lights will be slightly worse than with the MarsHydro Mars Pro II Epistar (when comparing the same watts per square foot).
This comes as no surprise as the light intensity (PPFD) of this light is the lowest on the list (still decent though).
The build quality of this light is also slightly worse. But it's also quite a bit of a cheaper light than the other lights on the list!
This is the cheapest grow light on the list.
Go cheaper than this, and you'll probably waste money on a subpar light. The VIPARSPECTRA Reflector is the cheapest you should go with a LED grow light.
Even though the VIPARSPECTRA covers the full PAR spectrum, including the green spectrum, plus the far-red spectrum (for the Emerson effect), when you look at the ratios, you'll see the blue spectrum has the highest proportion of the light's output.
What this means is that especially in the flowering stage (in which the green to red spectrum is most important), you'll find this light can disappoint compared to the other lights on the list. So don't be expecting miracles from this light in the flowering stage.
But because its price is so low, you can easily get a few VIPARSPECTRA lights, for the same cost as a high-end light like the Gavita Pro 1700E (keep in mind that 2 Viparspectra lights still won't give an as good of a result as one high-end light like those from Gavita or Horticulture Lighting Group).
If you're looking for a budget-light, I still recommend the MarsHydro Mars Pro II Epistar as the number 1 budget-light.
It's higher quality in all aspects, and MarsHydro has been around longer and built a more solid reputation as a manufacturer of budget LED lights.
But if you're looking for the cheapest of the cheapest, which will still get you good results…
This is the light you should go for.
LED Light Accessories
Most lights come with a hanging kit.
But if not, you will need a way to hang your lights.
And the best way to do that is with some quality:
- Rope Ratchets – (Amazon)
These rope ratchets are sturdy as hell.
But again, most lights come with a hanging kit!
If you want to make things easy on yourself, you should also get a timer to control your light cycles:
- Honeywell Timer – (Amazon)
Otherwise, you'll have to manually turn on/off your lights, which is a hassle, trust me.
What to Look for And How to Rate LED Grow Lights
Light is the main ingredient for growing high yield plants.
But how can you rate the quality of light?
Well, it’s precisely the:
- Range and ratio of different wavelengths/colors of light,
- Your light’s intensity, and
- Your light's efficiency,
which are the most important when rating a LED light.
And the only true way to measure the range of wavelengths and your light’s true intensity is not by watts per square foot or lumens as most people think, but by:
- PPFD, and to a lesser extent,
- PPFD/Watt ratio.
Let me explain what these abbreviations mean.
What’s PAR and Why It’s Important
PAR stands for ‘Photosynthetically Active Radiation.’
And although some LED light manufacturers (wrongly) use the term PAR when talking about a light's intensity, PAR is not a way to measure the intensity of your light.
PAR is the range for all the different wavelengths/colors of light that plants use for photosynthesis.
For your plants to grow optimally, your LED light should have all the different wavelengths/colors of light that makeup PAR. But especially important are:
- The blue wavelengths (for vegetative growth), and;
- The orange/red wavelengths (for the flowering process).
Luckily, most LED manufacturers are aware of PAR and design their lights in such a way that most of the wavelengths/colors of light that fall within the PAR-range are present.
And the lights in this list have specific vegetation/flowering settings with optimized spectra for that particular stage in the growth cycle. and, you can quickly activate these specific settings with a simple switch.
This is also the main reason why LED lights are more efficient than HID lights (HPS and MH).
HID lights emit ALL the different wavelengths/colors all the time. This even includes wavelength/colors that fall outside of the PAR range!
What this means is that HID lights waste quite a lot of electricity, because they're using power for colors/wavelengths that fall outside of the PAR range and thus are useless for your plants!
If you get the right LED light, your light will mostly have the wavelengths/colors of light that fall into the range of PAR and wavelengths that fall into the deep and far-red spectrum (which are essential for the Emerson effect). Your light will largely emit light that's actually being used by your plants for photosynthesis. This way, little to no electricity goes to waste.
But as you now understand:
PAR doesn’t say anything about the light’s intensity (in all these different wavelengths). Your light's intensity is key to rating a grow-light and getting strong plants with monster yields as well.
What’s PPFD and Why It’s Important
PPFD stands for ‘Photosynthetic Photon Flux Density.’
PPFD is a measurement of light intensity, and it says how many light photons that fall within the PAR-range (expressed in micromoles) hit a given square meter per second: μmol m(-2)s(-1).
A photon is the most basic and smallest unit of light.
Essentially, what PPFD does, is measure the intensity of your light.
This means to rate the quality of a LED light, PPFD is one of the most critical metrics.
Of course, there are also metrics like:
- Build quality;
- How much heat the light generates and its thermal management;
- Reputation and reliability, and;
- Customer service;
That you should consider when choosing a LED grow light.
But PPFD is what mostly matters to your plants. And what matters most are the PPFD values in the orange/red wavelengths, because these are the wavelengths that have the most impact on your yield in the flowering stage of your plants.
Below is shown how much PPFD is needed as a minimum for your Cannabis plants to grow and give you at least some yield:
- 255 μmol m(-2)s(-1) – 347 μmol m(-2)s(-1) PPFD on a 24 hours light schedule.
- 383 μmol m(-2)s(-1) – 520 μmol m(-2)s(-1) PPFD on a 18 hours light schedule.
- 510 μmol m(-2)s(-1) – 694 μmol m(-2)s(-1) PPFD on a 12 hours light schedule.
I can't emphasize this enough:
The guideline above is the minimum PPFD you'll need to produce a decent yield.
Your plants will grow and yield at a much better rate in the flowering stage if you get close to the optimum PPFD value between:
- 700 – 1500 μmol m(-2)s(-1)
The range above is the range where your plants will thrive in the flowering-stage on anything except a 24-hour light schedule, but a 24-hour light schedule isn't the best practice anyway.
But keep in mind this is the average PPFD value.
For optimal results, you never want your PPFD to drop below 510 μmol m(-2)s(-1) and never to go above 1500 μmol m(-2)s(-1) at any given point of the coverage area.
The exact optimum PPFD value is a controversial subject, and is among other things, highly dependent on:
- Whether you're supplementing with CO2;
- The growth stage in which your plants are: in the flowering stage your plants will need more intense light;
- Your specific strain: Sativa-dominant strains thrive under more intense light than Indica-dominant strains, and;
- Your light cycle: the longer your period of light, the lower the optimal PPFD value is and vice versa.
Can a light be too intense?
The threshold of ‘too intense' light is above 1500 μmol m(-2)s(-1). The exact value is also dependent on several factors like CO2-levels, your strain, and temperature. But you won’t get very quickly close to threshold with the lights on this list (as long as you respect the minimum height distance as advertised by the manufacturer, more about that later).
There’s a HUGE ‘but’ with PPFD though…
Even if we know the PPFD of a particular LED light, we usually don’t see how it was measured.
If you measure the PPFD in the area RIGHT below the light (in the center), you will get different values than further to the sides and corners. The further you get from the center of your LED light, the quicker the PPFD values drop.
You will also get different PPFD values if you measure from different heights. The closer you measure to the light, the higher your PPFD will be.
So when reading PPFD values, it needs to be 100% clear what:
- The distance was between the LED light and the canopy (or simply the floor);
- What the PPFD values were in the different parts of the coverage area, not only the center, and from different heights, and;
- The PPFD values are for the different wavelengths within the PAR-range (this one is tricky and is almost never provided, but in an ideal world we would have this info as well).
If you have the PPFD values, including all this information, you have a reliable PPFD measurement, and you'll know for sure how one light compares to another regarding light intensity.
But the sad truth is:
Most LED light manufacturers don't provide all these PPFD-reading-related background information.
Either they provide no PPFD values at all or a general PPFD value, with no background information.
A single PPFD value without any background information is useless information, as it doesn’t tell us exactly about the light’s spread, its penetration or even its intensity.
Note: Some LED manufacturers do provide PAR value charts (PPFD charts) of the light's coverage area. It's always worth it to ask for such a chart. Here's how such a chart looks like:
If you want an amazing yield, the PPFD should never drop below 510 μmol m(-2)s(-1) in the flowering stage. And as you can see, although the light gets advertised with a 4×4 ft. coverage area, should you grow according to the 510 μmol m(-2)s(-1) rule, it would only cover between 2×2 ft. and 3×3 ft. So always take the coverage area of the manufacturer with a grain of salt.
If PPFD isn’t 100% reliable either…what’s left?
We don’t wholly toss away PPFD in the garbage can.
Although it’s not the most reliable metric because of the often-lacking background information, it does say something (depending on the degree of transparency of the LED light manufacturer).
But if we want to get a complete picture in a world where LED manufacturers don't provide reliable PPFD measurements…
We’re also simply going to have to look at the results of different lights in different growing setups, which means reading and comparing lots of grow journals.
And EVEN this rating process has many caveats.
You can’t just compare one setup to another, there are countless variables that impact the yield of a grow beside lighting.
Nonetheless, when we compare similar grow setups, where only the LED light used, is different, we can verycautiously conclude which LED lights provide a higher yield than others.
So when rating the quality of the light that comes out of a LED grow light, these are the things we look at:
- PAR: which wavelengths have the highest output by the light. You want blue and red wavelengths mostly, but not only! You want the full PAR spectrum, including the greens. Plus the far-red spectrum (which falls outside of PAR).
- PPFD: are there any values provided for different wavelengths in the PAR-range and do we know how it's measured and calculated.
- Grow journals: compare the yield of in the same setups, where only the light differs (has many caveats as well!).
The bottom line when rating LED lights is:
Scientifically and 100% objectively rating LED lights is quite tricky at this time.
If manufacturers brought out independently tested PPFD measurements with all the before mentioned background information, it would be easy.
Nonetheless, using PAR, PPFD and grow journals, we can get an excellent idea of the quality of light coming out of a particular LED light.
Now you know how at least the quality of light coming out of a LED light should be rated, it’s time you understand how many watts to get for your specific space/setup.
Although watts per square foot doesn't say much about the light's intensity, it currently is a decent way to decide how big and powerful of a light you need to get for the size of your specific grow setup.
Unless of course, you've got reliable PPFD / PAR value charts, but you probably won't!
How to Choose a LED Light for Your Specific Setup Using Watts
As a general guideline, you should try to get a minimum of 50 watts per square foot with a LED grow light. This guideline is by no means perfect but will help to get you started.
50 watts per square foot means that:
- A 400W LED grow light will cover a 2.5 X 2.5 ft space.
- A 900W LED grow light will cover a 4 X 4ft space.
- A 1600W LED grow light will cover a 5 X 5ft space.
But here's the kicker:
I'm talking about the real wattage value! Im talking about the actual power draw, the actual watts that your light pulls out of the wall.
Let me explain.
Many LED light manufacturers give their specific model a name like ‘MARS II 400W'. The confusing part here is the ‘400W'. A MARS II 400W does not have a real wattage value of 400. Its actual power draw is 162 watts.
So ALWAYS look for the true wattage value/actual power draw of a light.
Don't get confused by the name of the light.
Below you can see an example of what I mean:
Example: This means that with a 3×3 ft. space (9 sq. ft.), you will need at least 9×50 = 450 watts of actual power draw.
Why does all of this matter?
Most lights get advertised with a coverage area that's grossly overstated not only when keeping the minimum of PPFD of 510 μmol m(-2)s(-1) rule in mind, but also when keeping the minimum of 50 watts per square foot in mind.
What's the bottom line when choosing a specific LED model?
There are 2 ways you can choose a specific model:
- Best method: You have PPFD / PAR-value charts, and you make sure that no part of your growing area goes below a PPFD of 510 μmol m(-2)s(-1);
- Realistic method: You don't have PPFD / PAR-value charts, and you go for a minimum of 50 watts per square foot.
The first method will result in a better quality yield but will be more expensive (you'll need more ‘light' to achieve this), and you'll need reliable PAR-value charts which are often not provided.
The second method will result in a decent yield and will be cheaper and easier most of the time (most LED manufacturers don't provide PPFD / PAR-value charts…yet).
Also, do realize the following when choosing a specific model:
In many cases, it’s better to get multiple lower wattage LED lights instead of getting a single high wattage LED light, and position them in such a way that light from different angles covers your plants.
This is because LED doesn’t have the best spread compared to other types of lights, and the more lights you have, the better you can position them and the better the spread of your light will be.
One last topic before we get to the 5 best led grow lights:
What's the right distance to keep your LED lights from your plants
It’s crucial that you put your lights as close as possible to your plants, without causing light burn, because this will directly affect the potency of your buds.
But it's just as important not to put your lights too close to your plants.
But what’s ‘too close’?
This is highly dependent on the light's brand and model.
The more powerful the light, the higher the minimum distance between your light and your canopy is.
LED manufacturers always provide minimum distances with their products, and you should use these.
Ultimately, you're going to keep a close eye on your plants and act accordingly:
- Raise them in a few inch increments when they show signs of stress/light burn, and;
- Lower them when you feel your plants need more intensity.
One Last Word
You don’t have to go for a premade LED light.
If you’re tech-savvy, you could build your own LED kit.
There are many guides and tutorials on the web, which will show you how to build a potent LED light that will be quite a bit cheaper than the premium premade LED lights, but will provide close to the same quality of light.
Just prepare and take your time to do all of your homework in case you go this route.
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