LED grow light buying guide

Growers switching from HPS to LED  confirm that the shift has had a positive impact on their plants. Generelly thrive and respond better to LEDs compared to conventional lighting fixtures. What exactly makes grow light better, is out of the scope of this article, we have it covered in another article though. In this article, we will introduce you to a checklist consisting of very important information  to compile before searching for a light system.

If you have questions concerning which LED grow lights to buy, how to use them and which company have the best products, then stay tuned, we will give you all the answers you need so you can choose the best LED grow light for your need.

Keep in mind that, this article is written based on the premises that you have already picked LEDs over any other light systems available. This means that we will not be going into details with HPS, CFL, MH and so on.

Growers who have switched from HPS to LED are most likely to confirm that plants thrive and respond better to LEDs compared to conventional lighting fixtures. What exactly makes grow light better, is out of the scope of this article, we have it covered in another article though. In this article, we will introduce you to a checklist consisting of few very important information points to compile before searching for a light system.

What exactly makes grow lights better, is out of the scope of this article. In this article, we will introduce you to a checklist consisting of few very important information points to compile before searching for a light system.


Checklist before buying

1) Consider your Budget

2) Determine the size for your indoor garden. Footprint and height.

3) Your growing needs. Plant type and phase.

4) How much time do you have?


The checklist above is a good way to summarize your requirements. It is true that LEDs are generally more expensive than other grow lights (HPS, MH, etc.), but you also get value for the money. An LED fixture typically comes with features like:

  • Integrated cooling system
  • Longer lifespan
  • More light emission
  • Less electricity consumption
  • Low profile, making them perfect for height restricted spaces

We encourage you to do more research on LED vs other light fixtures. Let us say, you have browsed through different options and you decided an LED is an investment you want to make, then it is time to choose which unit is going to be best for you.


Area coverage – How much watt do you need per square meter?

We will start by looking at the footprint. Most of the LED manufacturers inform the “core, veg or bloom/flower coverage”. Do not rely too much on these numbers.

Wattage is a relic of the HID (MH and HPS) days and it should not be the metric for measuring the usefulness of an LED grow light or calculating light footprint of an LED grow light. Wattage is a relic of the HID (MH and HPS) days. It should not be the metric for measuring the usefulness of an LED grow light. However, you can use wattage numbers of LED to estimate how much power (watt) you need per foot.

Here is how you can use wattage to estimate which LED grow light is enough to cover your grow area.

How much LED watt per foot you need depend on the type of your plant and its life stage. If you need to cover a plant in its flowering stage, you will need approx. 50% more watts per foot compared to if its vegging.

Average LED grow lights draw 32 watts to cover 1 sq. foot of flower plant. You can use this as a baseline to determine how many watts your LED unit need.

This means if you have a grow room of:

2 x 2 feet = 4 square feet. You will need a fixture that draws at least (4×32) 128 of actual watts*. 4 is the square feet of the grow area, 32 is the approximate amount of watt a flowering plant needs per sq. foot. *We are talking about actual watts, meaning watts drawn at wall, not the advertised wattage which typically comes in the name.

For larger spaces, just multiply 32 watts times your area in square feet and you will get the amount of actual wattage.


So you know you are ready to purchase an LED, and you know how many and what size you need, now which one to buy?


What does wattage mean for LED grow lights

Most buyers out there looking for an LED grow light tend to fall in the same marketing trap. In order to become just another sheep falling the wolf trap, there are a couple of key things to understand.

  1. LED manufacturers label their products with a high watt number for example King Plus 1000w. Just because it is called that, doesn’t mean it actually is true. Disregard the watt in the title! Here is why:

Under product description, it is said, that you have 10 pieces of 10-watt LEDs. So that means you have a total of 1000 watt, right? Nope! It simply means the unit has a max driven capacity of 1000 watts.

When you drive a light fixture to its max it will produce excessive heat which the components within the unit are not built to tolerate. This will shorten the units’ life span significantly. So, most LED manufacturers only drive the units to a fraction of its max capacity to maintain a fine line between performance and reliability. They can also use different titles to market the same product. For example, a 1000w LED grow light can also be called a 300 watt. The key here is to look at the actual power draw.

The key here is to look at the actual power draw.



LED chips

LED chips come in several wattage outputs ranging from less than 1 watt up to 100watts. The higher watts the more expensive the chip. The most common sizes in a grow light are 1,3, 5 or in this case 10-watt chips. High watt chips are better suited for applications that require more penetration. For example if you have a tall leafy plant then you need more penetration so the light can better reach the entire plant. However, in case of a more low-profiled grow or cloning even 1-watt chips will do the job as long as you don’t go over 3-watt chips.

Chip companies

Not all LED chips are alike. Some are known for their high-performance and long lifespan whereas others have a less reassuring reputation. LED chips are manufactured widely around the globe. The ones which you and I are most likely to encounter are typically put together in the US, Europe or China. Now among the horticulture communities, it is widely accepted that the better-quality chips are going to be US made, names like CREE and Bridgelux are considered the leaders in LED research and manufacturing.


Spectrum and Light

There is a lot of ground to cover here, but to keep it relevant to your buying intend I will not be going to details with the science part of this. Important things to note here, is that plants perceive light different. Light is one of the sources necessary for plant to convert co2 into food for itself. This is also called photosynthesis. Only a portion within the full spectrum of light promotes photosynthesis. This is called the PAR zone. When led manufacturers provide the spectrum informations. Make sure to check where the wave lengths of light are on the full spectrum.

For example let us have a look at the king plus 1000 w.

This graph tells us that the king led fixture utilizes the electricity to emit light which is within the PAR zone of light spectrum. This means, it is very limited how much consumed electricity goes to waste.

Moreover, we can see that the light is peaks at the red end of the spectrum. What does this tell us? This tells us that the emitted light is mostly focused in red color which is most ideal for the flowering stage of plant life. Or to encourage a plant to enter the flowering stage.

So, this light fixture spectrum graph tells us that the fixture is most ideal for a plant in its flowering stage. Or a plant in preflower stage. For vegging, you want a fixture that emits more light on the blue on end of PAR spectrum.

Okay so the spectrum is within the PAR range , good. So is that it? No. not quite. One thing is the PAR value of the light tells us how much light is emitted from the fixture, but how much of it does actually land on the plant canaopy is a different matter. Not to mention a very important matter. It is called



We got the spectrum covered. From what to take with you from there is that, you want to look for a led grow light fixture that emits wavelengths of light between 400-700 nm. Also called PAR (photosynthehtic actve radioton) light. Basically, it means that the light emittet from a given fixture, is the sort of light that support plant life. Important thing to remember here is that the PAR is not a unit of measure, like kg, feet or inches etc. to find how how much life given light the fixture emits, you need to measure its PPF (photosynthethic photon flux density. The PPF tells us the total amount of PAR produced by a lightning each second. The unit for this is (umol/s) so when looking for a grow light, look for the PPF expressed in umol/s to find out how much PAR light it produces.



PPFD (fokuserer istedet på noget simpler som er mere relevant for buyeren. Brug måske PAR per WATT. I stedet for at bruge alle de begriber som forvirrer kunden alligevel.)

This is another important metric to understand and keep in mind when looking for the best grow light.

PPFD stands for photosynthetic photon flux density. This measures the amount of PAR which actually arrives on a given surface umol /m2/s.



There are a bunch of internet vendors out there either drop-shipping lights from China or runs a so-called “one-man operation”, where the only thing they do is to move it from manufacturer to the costumer. The units can be good as long as it runs well you don’t have any problems. If it happens that your unit breaks for whatever reason, or you experience malfunctions with the driver, fan, lights and what not, then the warranty quality comes in to play.

You want to make sure that the company you purchase the LED from are reliable when it comes to warranty.  Let us have a look at an example of bad warranty vs good warranty.

Bad warranty policy

  • If a shop asks you to send the light back and THEN they will send you a replacement.

Good warranty policy

  • They send a replacement out first and even let you use its box to return the broken unit while at the same time covering the postage.
  • The longer the warranty the better.


Now guaranty is different. It basically means the time period after the purchase in which you can get full refund upon returning the unit. For example, if a company have 3 months gurantee and 2 years warranty, it means you can get your money back within 3 months, but the will provide services in case of errors for up to 2 years.

What is important to take with you from this paragraph is, like many other purchases, it is always a good idea to do some research on warranty and guaranty. A 5-minute research now, can save you a lot of headaches, not to mention cash, on the long run! You can start by reading some reviews or google the company name. If you still haven’t found what you are looking for, then why not call the customer service and ask them the following question:

1) How long is your warranty?

2) What is your replacement procedure?

3) Are your units in stock, or do you drop-ship them from the factory?

5) Ask for details on the light, number and type of chips, actual wattage, recommended core coverage and height above canopy etc..

6) When will this unit ship, and when can I expect to have a tracking number?


In this article, we covered all the aspects to consider before purchasing an LED grow light. Hopefully by now you have a better idea of what to look for when browsing through the catalog, site or whatever you browse through when you look for these things. In case you missed it, here is a summary of what we covered.


  1. Don’t pay attention to the watt numbers, look at the actual watt.
  2. Use 32w per foot as a baseline to estimate the size of grow light. Example: if you have a grow area of 2×2 which 4 square feet, you need a grow light which draws at least 4×32=128w actual power.
  3. Consider the PAR light produced per watt and the light spectrum chart. This is the most crucial metric for determining the quality of the fixture.
  4. Prior to purchasing, make sure to research the companies refund and warranty policies.

The intentions of this article were to provide you the essential information you need to better navigate through the data jungle out there and find the best LED grow light suited for your needs.

If you feel like you know more than you did before reading this article, and you find the accumulated knowledge is relevant to what you have been searching for, then it is safe to say that our goal has been accomplished.

Leave a Comment