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.

This article explains the basics to understanding grow lights and the most common terms used when measuring and comparing specifications and performances.

The focus will be on lights in the lower end of the LED grow light price range. After reading this article, you should be able to distinguish poorly built LED grow lights from good LED grow lights.

General Awareness of LEDs

The 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 often found in the business is that some brands don’t reply to customer questions or emails. I 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 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 a North American, Australian/New Zealand, or European home base.

If a product looks generic and the same (or very similar) to a design that’s used widely across different brands, it’s also a common sign of a suspect brand. While a seller’s base isn’t necessarily a deal breaker, it leads to the next point.

Read also: How To Set Up Your LED Grow Light

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 that goes into making 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 “1,000W Grow Light,” “Super High PPFD/PAR,” or similar claims online. Consumers rarely try 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.

One 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 1,000W, 1,500W, or greater values. For inexpensive grow lights (less than $500), this 1,000W 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 “1,500W 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 1,000W+ claims made by some brands 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.

Or, they refer to the total wattage of the fitted diodes. For example, 100 diodes at 10W each equals 1,000W. The problem with this is that a high diode wattage doesn’t speak about the lamp’s performance.

Theoretically, a 10W or 15W diode could produce more light than a 3W but looking at the draw power for these “1,000W” and “1,500W” lights, we see that they consume about 150-200W. This means they are running at around 15 per cent of max capacity (150W draw power/1,000W total LED wattage = 0.15 = 15 per cent). Smaller diodes, with good heat disposition, can run at 50-60 per cent capacity.

A 10W diode at 18 per cent capacity will draw 1.8W (10W*0.18 = 1.8W). A 3W diode at 60 per cent 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 “1,000W LED grow light,” so some brands opt for large diodes.

The bottom line? Less heat (lower operating temperature) equals longer lifespan.

Read also: 10 Mistakes to Avoid When Using LED Grow Lights

Understand Your Needs

Budget
This is 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. 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 (less than $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.

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.

Not every square inch 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. 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 one to two square feet 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.

Light Output and Intensity (PPFD/PAR)
Your plants need a certain amount of light to grow. To keep this guide short and on point, weed plants, for example, 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.

PPFD basically means photon density; how much light hits a certain area every second. So, high PPFD means high light intensity.

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 per cent blue light, 15-25 per cent green light, and about 60 per cent 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 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.

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.

Read also: Red Light, Blue Light: Balancing LED Efficiency with Performance

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:

  1. Efficacy
    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.

    Example: 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 per cent more efficient at turning electricity into light and effectively will emit 50 per cent more light per consumed watt.

    Generally speaking, budget lights will perform at around 0.8 to 1.5 umol/J. High-end lights (usually more than $500) can reach efficiency ratings that are twice as high.

  2. Spectrum
    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. 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 pinkish (less heavy on blue and red) is the ideal choice for both plants and humans.

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

Think critically and don’t 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 to 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 I’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.