How To Find the Right Indoor Light on Amazon, Ebay, and Walmart
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 the lights' specifications and performances.
Our focus will be on lights in the lower end of the LED grow light price range, around $100-200.
Look up the brand; website, socials, responsiveness
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 (eg. CNN), there are plenty of fake or bought reviews floating around on Amazon. Apply critical thinking!
Location-based? China, US, EU?
It's no secret that the American and European online marketplaces are getting flooded with brands from all over the world, primarily from China. While "Made in China" doesn't reflect the products' quality (I mean, even our expensive phones, laptops and TVs are all 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: product/listing title, images, and the describing text. Phrasing, sentences, and grammar will be a bit off and just by reading a couple of lines the signs are there; subtle but visible. If a product looks generic and the same (or very similar) design is used widely across different brands it's also a common sign of non-US/EU 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).
... do the sellers know what they are 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 substitute test plants, but even this is done at a very small scale.
To conclude this point: 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.
How reliable is the lamp's 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 sensors are required to accurately measure light intensity (PPFD in µmol/m2/s) which 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'd 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 with watt (W) claims. 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; 0.2W, 0.5W 1W, 1.5W, 3W, 5W, 10W, 15W, etc, and some brands like to count the total number of diodes and multiply it with the diode wattage. Eg. 100 diodes at 15W would be presented as a “1500W light”.
While two diodes of the same size can vary in efficacy, the general truth is that the smaller the diode, the more efficient it is (not including COB technology).
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).
What really matters is how much light a grow light emits and the only accurate way of measuring light output and where that light actually lands is by measuring the PPFD.
Understand your needs
This is pretty straight forward. 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 1-2 plants. Around $150-200 for a light that covers 2-4 plants.
If growing a high-value crop you quickly recoup the investment after a 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: higher grow light price = more light = better coverage = more plants = bigger harvest. Pretty logical. 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 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)
Ask yourself, how many plants do you intend to grow? How big are they expected to grow? How large 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-US 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.
If you're growing cannabis, Indica strains grow smaller than sativas 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.
Beginners that are still learning plant management will likely have smaller cannabis plants, around 2 square foot (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.
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)
Your plants need a certain amount of light to grow. To keep this guide short and in point, your weed plants will need around 300 PPFD (sometimes also incorrectly referred to as PAR) when they are small and in their vegetative stage, then about the double (600 PPFD) during flowering. Light will still be utilized beyond this level of intensity, but less and less efficiently. Experienced growers are often aiming for upwards 900 PPFD and with added CO2 and the right ratio of nutrients, temperature, and humidity, cannabis plants can take even a bit higher PPFD levels but 600-900 is still a good general rule of thumb.
Smaller plants like herbs (basil, rosemary, and microgreens) require about 150-200 PPFD for good results while veggies (cucumbers, peppers, tomatoes) need a bit more, 200-600 PPFD.
PPFD basically means photon density; how much light hits a certain area every second. More on PPFD here.
High PPFD means high light intensity. To put it plainly; see this as sunbathing at the beach. If you'd go to the beach in north Canada you'd get less tan (low PPFD) than going to the beach in southern Florida (high PPFD). To get tan you need plenty of (sun) light. Same thing goes for plants but the light is measured in PPFD.
Light color spectrum
While this varies slightly between different plants, the general consensus is that most plants grow best under light with a full color spectrum: blue, green, and red light. Some LED grow lights have a color spectrum with a mix of single colored diodes. Other lamps will have diodes emitting a white light. White light contains all colors and mimics sunlight to some extent.
Light is fundamentally photons; light particles with a certain wavelength (color). Light color is measured in wavelengths, 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.
LEDTonic Z5's light spectrum
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.
Lamp efficiency and watts (efficacy in µmol/J or PPF/W or PPE)
You want a grow light that is efficient; high efficacy, measured in µmol/J (or PPF/W or PPE, same thing, different names). An efficient light will be able to put out (emit) more photons (light) per consumed electricity (watts, W). 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 (drawn) watts somewhat correlates to more light output, but there are TWO additional important factors to add into the mix: (1) efficacy and (2) spectrum.
1. Efficacy means the grow light's efficiency in turning electricity into light. High efficacy, measured in µmol/J or PPF/W means the lamp is better at converting electricity to light.
Grow light A consumes 100W and has a 1.0 µmol/J rating.
Grow light B also consumes 100W but has 1.5 µmol/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 1.6 µmol/J. High-end lights can reach twice as high efficacy ratings.
LEDTonic Z2’s efficacy is 1.6 PPF/W (or umol/J) as shown in the test report.
An example sometimes use to describe efficacy is to compare with the size of a car’s engine. Just because the engine is big doesn’t mean the car will go fast, but the engine will definitely burn a lot of fuel. 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.
2. The above example is correct assuming both grow lights have the same color spectrum. I.e. 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/yellow-ish 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. I.e. the diodes have lower efficacy.
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 photons, 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 a better choice for both plants and humans.
A long-lived myth is that plants are green because they don't use these wavelengths and instead reflect all green light. This is not true. Plants are green because they reflect more green light than blue or red, but they still absorb the majority of all green light. In other words, plants use all wavelengths between 400-700nm for photosynthesis.
Plants' leaves are complex structures. Blue, orange, and red photons are absorbed slightly more efficiently than green light, but there's more to it than this. Blue and red photons are absorbed easier than green photons and will drive photosynthesis more efficiently in lower light intensities but this is mostly concentrated to the surface layer of a plant's leaf. As light intensity increases from low and medium, to high, the leaves surface gradually becomes light-saturated and instead of being used for photosynthesis, additional absorbed photons are turned into and dissipated as heat. Green light penetrates deeper into leaves tissue than blue and red, and reach parts of the leaf that haven't been saturated yet. On the downside, green light is both less efficient to produce electrically and less efficient at driving photosynthesis in lower intensities. This means that the benefits of adding green light primarily come into play at high light intensities, especially when comparing with other light colors, like blue and red.
Therefore, creating a lamp that is both efficient at producing photons and that drives photosynthesis effectively is a balance. We want to create as many photons as possible per watt while stimulating accessory pigments such as carotenoids and without saturating the leaf's surface completely with only blue and red, leaving deeper parts of the leaf unused.
We've constructed our Z2 and Z5s spectrum based on this information and are balancing between the greatest output of photons and quality of light, for both our plants and us. For our lamps and the way they are intended to be used, this results in a slightly pink spectrum. A balance that is not tied to one specific plant, grower or growing style, but a balance that will work for all situations and plants.
So, to determine lamp efficiency of a grow lamp, compare the spectrum (make sure it's well balanced) and efficacy (µmol/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 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.
Cross-reference information: compare Amazon listing to website, Youtube, socials.
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 it. Sometimes an email to the manufacturer asking how they did their test and provide any kind of evidence is enough. Best way is obviously to see indisputable evidence in the form of video test reports that cannot be faked or modified.
Understanding the basics of how lights work and knowing what numbers to look for is necessary for you to make a smart purchase decision.
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