It's a real jungle out there. There are just pages and pages with LED grow lights of various shapes, forms, sizes and prices. Some brands make ridiculous and confusing claims about their lights. Other brands withhold crucial information, which makes it difficult to compare one light to the other. We'll teach you what to look for, what to look out for and how to compare one light to the next.
We'll also explain the basics to understanding grow lights and the most common terms used when measuring and comparing specifications and performances.
Our focus will be on lights in the lower end of the LED grow light price range, around $100-200. After reading this article, you should be able to distinguish poorly built LED grow lights from good LED grow lights.
Our first tip? Look up the brand, including its website, social media and online reputation.
If you're going to spend a significant amount of money on a grow light, you want to be sure you're buying it from a good and reliable source. When you find an interesting light on Amazon, for instance, look up the brand elsewhere. Do they have a website? Do they have social media channels? Can you reach them on Facebook or by email? A complaint we often see in the business is that some brands don't reply to customer questions or emails. To us, this is ridiculous as we feel that a fairly expensive product should also come with good after-purchase care.
One more thing: a high review count on Amazon doesn’t always equal a good product. As several news sites report, there are plenty of fake or bought reviews floating around on Amazon. Apply critical thinking!
Location, Location, Location
It's no secret that the American and European online marketplaces are getting flooded with brands from all over the world, primarily China. While "Made in China" doesn't reflect a product's quality (even our expensive phones, laptops and TVs are made in China), it speaks a lot about the seller and the way they do business. It's usually easy to get an idea of the seller's location and origin simply by looking at a product's description, including product/listing title, images and the describing text. Phrasing, sentences and grammar will be a bit off with brands that don't have an American or European home base, and you can figure it out just by reading a couple of lines.
If a product looks generic and the same (or very similar) to a design that is used widely across different brands, it's also a common sign of non-U.S./E.U. brand. While a sellers' base isn't necessarily a deal breaker, it leads to my next point…
Generic lamps, generic lamps everywhere (brand names crossed out).
The Seller's Knowledge
Do the sellers know what they're talking about? Do they grow themselves?
Manufacturing a light is not that difficult. However, putting together a light that is good and efficient is harder. A grow light should be practically tested and used to determine how well it works. In many parts of the world, China for instance, growing cannabis is a big no-no. Some plants (tomatoes) have very similar characteristics to marijuana and could, to some extent, be used as a substitute test plant, but even this is done at a very small scale.
Find a brand that knows what they are doing, knows how to grow and knows the product they are selling. There's quite a lot to it to make a good light. If a brand can't present their product well, it's a sign that they don't fully understand it or its use.
Reliable Information and Specs
It's easy enough to write "1000W Grow Light", "Super High PPFD/PAR" or similar claims online. Consumers rarely try or are able to verify this. Expensive testing equipment such as Apogee quantum meters are required to accurately measure light intensity (PPFD), but they aren't an economically viable option for small-scale grows or hobby growers.
Our suggestion is to cross-reference the specs and information on as many different sites and places as possible. Ideally, you'll want to see videos of live recordings and testing, or testing by independent users that are knowledgeable in the field.
It's also important to know which values to look for. A typical misleading trick is to boast wattage claims of 1000W, 1500W, or greater values. For inexpensive grow lights (<$500), this 1000W value will never reflect the consumed watts (draw power) but rather the total wattage of the chips/diodes used in the light.
Diodes come in various sizes; 1W, 1.5W, 3W, 5W, 10W, 15W, etc., and some brands like to count the total number of diodes and multiply that by the diode wattage. For example, 100 diodes at 15W would be presented as a “1500W light”. The truth is that the smaller the diode, the more efficient it is. This is important to keep in mind and this claim can also be verified in plenty of other places online.
The 1000W+ claims some brands make either refer to which HID/HPS lamps their LED light could replace, which is highly inaccurate as there really is no reliable way of comparing HID/HPS to LEDs out there other than light coverage and intensity (more on this later).
Or, they refer to the total wattage of the fitted diodes, for example, 100 diodes at 10W each = 1000W. The problem with this is that a high diode wattage doesn’t speak about the lamp’s performance. As mentioned previously, not only does higher wattage mean a less efficient the diode, but large diodes also produce a larger amount of heat. This means they need to be run at a lower maximum capacity.
Theoretically, a 10W or 15W diode could produce more light than a 3W but looking at the draw power for these "1000W" and "1500W" lights, we see that they consume about 150-200W. This means they are running at around 15% of max capacity (150W draw power/1000W total LED wattage = 0.15 = 15%). Smaller diodes, with good heat disposition, can run at 50-60% capacity.
A 10W diode at 18% capacity will actually draw 1.8W (10W*0.18 = 1.8W). A 3W diode at 60% capacity will also draw 1.8W (3W*0.6 = 1.8W), meaning the total light output of these two diodes will be roughly the same. But it’s obviously much less sexy to write “300W LED grow light” than “1000W LED grow light,” so some brands opt for large diodes. See what I mean by misleading information?
Here’s an example of a popular light that makes false claims and also boasts with misleading information. 185W consumed/1000W diode wattage = 0.185 = 18.5% of max capacity in average per diode. 18.5W output per diode, similar to a 3W diode but 3W generate less heat.
The bottom line? Less heat (lower operating temperature) equals longer lifespan.
Understand Your Needs
This is pretty straightforward. How much money do you want to spend - or can afford to spend - on a light? You typically need to spend about $100 for a grow light that produces enough light for one to two plants, and around $150-$200 for a light that covers two to four plants.
If you're growing a high-value crop, you'll quickly recoup the investment after harvest but you may still want to start out with a reasonable budget. If you're growing primarily as a hobby, the price point of your light may be even more important.
A rule of thumb is this: Higher grow light price = more light = better coverage = more plants = bigger harvest
Pretty logical, right? A small and cheap (<$50) grow light simply can't be fitted with enough light emitting diodes to make any significant light impact on large plants such as cannabis. They may work well for smaller plants, such as herbs, spices and some veggies, but large plants will need a lot of light to bear fruit/buds. More on this later.
Here’s a picture of a marijuana plant (autoflower) that has already transitioned into its flowering stage but due to the lack of light it received, it’s tiny and doesn’t look very healthy.
Grow Area (Light Footprint)
How many plants do you intend to grow? How big are they expected to grow? How large of an area does your light need to cover?
As light (and water and nutrients) is your plants' "food," if they receive less than required, the plants will not grow to their full potential, as per the picture above.
Not every square inch (or square centimeter, for non-U.S. growers) of the plant needs maximum possible light coverage for the plant to thrive, but the majority (the more the better) of the plant should be well illuminated.
Indica grows smaller than Sativa in general, but it also comes down to how you manage the plant throughout its grow cycles. You can train the plant to grow a certain way and have a certain size or area.
Beginners that are still learning plant management will likely have smaller plants, around 1-2 square feet (~0.1-0.2 square meters) per plant, than experienced growers.
Find a grow light or a number of grow lights that cover the area of your grow. Sometimes, it makes more sense to buy two (cheap) lights rather than one expensive one.
The area a light illuminates should be specified by the grow light manufacturer. If this info is not available, it suggests the seller is either withholding information or doesn’t really know how to best use the light.
Here’s our LEDTonic Z5’s light footprint. The area marked with green is our recommended grow area. The tests were made in a 3x3’ tent. If using a 2x2’ (4 square feet area) tent, which we recommended, light will reflect off the walls and better illuminate the outer edges of the 2x2’ area, increasing the PPFD. More on PPFD below.
Light Output and Intensity (PPFD/PAR)
Your plants need a certain amount of light to grow. To keep this guide short and on point, your weed plants will need around 300 PPFD (sometimes also referred to as PAR) when they are small and in their vegetative stage, then about double (600 PPFD) during flowering. With added CO2 and the right ratio of nutrients, temperature and humidity, cannabis plants can take even a bit higher PPFD levels but 600 is still a good general rule of thumb.
Smaller plants like herbs (basil, rosemary and microgreens) require about 150-200 PPFD, while veggies (cucumbers, peppers, tomatoes) can take anywhere from 200-600 PPFD.
PPFD basically means photon density; how much light hits a certain area every second. So, high PPFD means high light intensity. For example, imagine sunbathing at the beach. If you go to the beach in northern Canada you'll get less of a tan than going to the beach in southern Florida. To get a tan, you need plenty of (sun) light. The same thing goes for plants, but the light is measured in PPFD. The video below explains how to measure PPFD.
Light Color Spectrum
Plants need a full spectrum of both blue, green and red light, similar to the sun.
Light is fundamentally photons, or light particles with a certain wavelength (color). Light color is measured in wavelengths by nanometer (nm). Blue light has the shortest wavelength of around 400-475 nm, then green (475-550 nm), yellow/orange (550-625 nm) and red (625-700 nm).
Various research says an ideal color spectrum for plants consist of 15-20% blue light, 15-25% green light, and about 60% red. This balance is optimal for plant growth, health and photosynthesis. The natural sun color spectrum has more green and yellow, and less blue and red, but plants actually thrive when boosting blue and red a bit.
Practically every brand and every grow light out there has a different spectrum (different ratios between blue, green and red). Most of them claim they have the "perfect full spectrum light" when the reality is different. Some brands even make this claim when they barely have any green light at all coming out of their grow light.
Here’s a picture from an Amazon listing that advertises the light as “full spectrum” but its spectrum chart clearly shows a spectrum with almost exclusively blue and red. Brand name crossed out.
In short; look for a color spectrum that has a decent amount of blue and green but a lot of red, as it's the red light that the plant craves the most. Looking at large-scale cannabis grow operations or industrial grows, you'll see that they never use BLURPLE (blue-red-purple) colored lights.
Lamp Efficiency and Watts (efficacy in umol/J or PPF/W or PPE)
You want a grow light that is efficient, or high efficacy measured in umol/J (or PPF/W or PPE, same thing, different names). An efficient light will be able to put out more photons per consumed electricity. Typically, grow lights in the cheaper price range ($100-200) will consume anywhere from 50W to 150W. This should be specified by the manufacturer.
More consumed watts somewhat correlates to more light output, but there are TWO important additional factors to add into the mix:
Efficacy refers to the grow light's efficiency in turning electricity into light. High efficacy, measured in umol/J or PPF/W means the lamp is better at converting electricity to light.
Grow light A consumes 100W and has a 1.0 umol/J rating.
Grow light B also consumes 100W but has 1.5 umol/J rating.
This means grow light B is 50% more efficient at turning electricity into light and effectively will emit 50% more light per consumed watt.
Generally speaking, budget lights will perform at around 0.8 to 1.5 umol/J. High-end lights (usually $500+) can reach efficiency ratings that are twice as high.
LEDTonic Z2’s efficacy is 1.4 PPF/W (or umol/J) as shown in the test report.
An example sometimes used to describe efficacy is to compare it with the size of a car’s engine. Just because an engine is big doesn’t mean the car will go fast, but the engine will definitely burn a lot of fuel. The same thing goes for LED lights. Just because a lamp has high draw wattage doesn’t necessarily mean it produces a lot of light. Look for both efficacy and power draw to understand a lamp’s performance and output.
The above example is correct in assuming both grow lights have the same color spectrum, or both grow lights emit light of the same color. If you take a quick look among grow lights, you will see that some lamps emit a light that is very blue, red or purple-colored, whereas your typical desk lamp or ceiling lamp emits a white/yellowish light, right?
Certain light colors, primarily blue and red, are easier to produce. Green, UV and far red, for instance, require much more electricity to produce.
Therefore, many grow light manufacturers opt to have a color spectrum of primarily or even exclusively blue and red light (see image above). While this will produce the maximum amount of light output, this spectrum is very imbalanced and not ideal for plants or for your eyes. It's an unnatural light and irritating to look at for long periods of time. A light color spectrum close to natural sunlight, or at least pink-ish (less heavy on blue and red) is the ideal choice for both plants and humans.
As mentioned above, various research says an ideal color spectrum consists of 15-20% blue light, 15-25% green light, and about 60% red for optimal plant growth, health and photosynthesis.
So, to determine the lamp efficiency of a grow lamp, compare the spectrum (make sure it's well balanced) and efficacy (umol/J, PPF/W, or PPE). You want a fair spectrum and high efficacy. Then look at how much electricity (watts) the lamp draws, how much light it puts out (PPFD) and how large an area it illuminates. Some lamps will have a high light output but they focus the light into a very small area. This is good if you only grow one plant but not ideal if you have a larger area to cover.
The Bottom Line on Buying LED Grow Lights
To finish off this little guide, I'd like to urge you all to think critically and not take any claims made online as facts unless you can verify them. Sometimes an email to the manufacturer asking how they did their test and asking them provide any kind of evidence is enough. The best way is obviously to see indisputable evidence in the form of video test reports that cannot be faked or modified.
Also, try to look up the same model in various places as we’ve seen highly inaccurate or variable information depending on the site/source.
Understanding the basics of how lights work and knowing what numbers to look for is necessary for you to make a smart purchase decision.