LED grow lights

I start my annual veggies etc. under an 8-tube HO fluorescent.

Sometimes I’ll start looking into the LED grow lights. The whole thing is so confusing. First off, they are obviously targeted to growers of a particular type of plant. One that I have nothing against, but I do not grow. :grin:

And the other thing is, it’s damn near impossible to tell what you’re actually getting. The “wattage“ advertised is not the actual wattage, but some attempts to say it’s “equivalent“ to a MH/HPS if that wattage. In my experience with LED, “equivalent“ wattage is usually overstated. A “1500 W“ LED light only consumes around 200 W of power, and I highly doubt that it’s really as bright as a 1500 Watt metal halide.

But they also don’t give a lumen rating or a PAR rating. How the hell do I know if what I’m buying is sufficient or will produce too little or even too much?


i have 2 600w viparspectras i use in my 5’ x 8’ grow room. they cover that area completely with some overlap. I’ve grown just about everything under them. the grow room stays about 80f in there when the lights are on. they are in the mid priced range for leds but I’ve had them for 4 years with no issues or noticeable loss or light brightness. they have pretty good ratings on amazon. under the description in there, they explain the lights par and intensity as you go out from the center under the light. check it out.

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I think the whites are better than the multi color and the best way is to judge growth would be to look at PPFD ratings of each light for total output. Or look at umol/j for an idea of how efficient it is. You want atleast 1.5 umol/j as a t5 is 1.8umol/j some of the newest leds go up to 3 umol/j and to give you an idea. Now wattage is really a measurement of heat that electricity can produce so you should look at total wattage and once you subtract the usable light spectrum whats left is heat. If what your buying is not giving you a actual rating its not a decent light.



I don’t know why people still make those videos. A PAR meter is not a plant. It tells you nothing about how well it will grow your plant of choice. I will be impressed when I see a practical test.

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@RichardRoundTree is rigth, whatever you do - do yourself (and your eyes) a favor and don’t get one of those purple lights.

With increasingly high efficiency LEDs wattage doesn’t mean anything. Consider how they have 60W equivalent (to an incandescent) LED bulbs that only use only 9 watts. So yeah, a modern 200 W LED light can be as bright as an 1500 Watt metal halide - but its not something that a typical consumer can test.

What you want is a lumens/Watt measurement or a PPFD map. On Amazon this seems like a decent option:

True, but its the best measure we have for light in the context of what plants utilize. If you want a comparison you want a practical example you can watch this: Viparspectra 300 vs. HLG 65 Quantum Board - Final Results - YouTube

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If anyone buys that one on Amazon grab a Kilawatt and a lumen reader and we can compare to the one I got on aliexpress.

6000W LED Grow Light Panel Full Spectrum Phyto Lamp 256 LED Grow Lamp AC85 265V For Indoor Grow Tent Plants Growth Light|Growing Lamps| - AliExpress

R&D MT30 Lux meter 0~200,000lux Range light meter pocket design illuminometer lux/fc photometer tester Enviromental Testing Grey|Spectrometers| - AliExpress

I have not bought a 9v battery to use it yet but when I do I’ll let everyone know.

The results speak for there selves something is going right so far. I started rooting these pomegranate cuttings since March 4th

Thank @alanmercieca

And these Luma cuttings

Thanks @swincher

And these Fig cuttings (which are not under direct light but as long as im showing off)

Thanks @JesseinMaine


My understanding is lumen readings are pretty useless for LED grow lights. Lumens are measuring brightness to the human eye, but grow light LEDs are designed to be bright only in the photosynthesizing part of the spectrum.

That’s why photosynthetic photon flux (PPF) is the better measure of brightness than lumens, so what you want is a meter to measure PPF density (PPFD meter) if you want to measure LED grow lights.

See, e.g.:



Many phones have sensors that can be used to measure light intensity. Ive got an app that measure LUX and while these apps arent ideal, they will work to compare grow lights with similar spectrum to each other. or help you set the intensity of your light based upon previous experience. For example if you found that X plant does great with a specific light when you have the light intensity at the top of the plants adjusted to 10,000 lux, thats fairly reproduceable if you keep good notes. You really cannot judge light intensity well at all by using your eyes because they automatically adjust to make most lights look similar to you, by letting less light into your eyes as the light gets brighter, need to use some sort of tool to measure and anything is better than nothing.

I have success starting a few tomatoes under a T-5 fluorescent light by Ferry-Morse that is, shall we say, minimal. Sold at Wal-Mart.

If I wanted to be more ambitious, I could easily start several dozen plants with a more serious fixture.

No need for those odd “blurple” lights.

That’s why I post here. I honestly didn’t know what tool to get to do test with and the lux meter was only 10 bucks.

A lux meter can still be very useful as a ballpark figure if you have enough light or to double check how high you should place your lights. For white light sources they can be within 10% of a real PPFD measurement.

Here are some rough values to aim for with a light that’s on 18hrs/day:

  • 15000 lux - starting seeds
  • 18000 lux - growing lettuce indoors
  • 25000 lux - rapid vegetative growth (eg. growing basil)

Lux meters are trash when it comes to measuring LED output they were made for measuring the sun and that is where they are applicable. Most leds look really good under a lux meter and when you grow plants they do not work really good.

While yes these lights grow plants my point is that a 315w CMH or a 1150w DE HPS or even a T5 with a new good bulb in it would grow them faster and better and would be a better use of electricity. That many of these LED lights saying they are more efficient in reality are causing higher emissions by requiring more electricity to do the same amount of growth.

Once again if the LED does not state PPFD or umol/j the thing is likely less efficient than a t5

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I’m not sure where you’re getting this info from. I will agree that the consumer market is flooded with garbage “grow lights”, but in recent years a decent quality ($100+) LED grow light can easily exceed efficiency of 2.0 µmol/joule and they continue to get better and reduce in price as LED lighting becomes more prevalent.

That being said for starting seedlings a T5 is fine if you have one, but otherwise a legit LED grow light costs less to operate.

I grow tens of thousands of seedlings every year under grow lights. I have looked diligently and nobody has yet built a grow light optimized for producing seedlings. Here are the specifications of a grow light that would do the job.

There has to be a mix of different LED’s to get the right spectrum. This includes red, blue, yellow, green, and a few Ultraviolet. That is approximately in order of number required.

One watt LED’s are ideal for the purpose. Do your own due diligence to find out why.

120 of the 1 watt LED’s mounted in a frame 4 ft by 2 feet would replace the 6 bulb fluorescent fixtures I am currently using.

Properly constructed, such a panel would dissipate heat evenly and would not require a cooling fan.

In the meantime, I purchased LED tubes made to replace fluorescent bulbs and used them very successfully to grow plants the last 2 years. The disadvantage of using LED tubes is that they consume too much power as compared to a dedicated LED panel.


I have a few of the full spectrum parfactworks panels and used them for my seedlings this year and they seem to work fine.

What is the deal with the COB lights? Something like this.

I just got my second grow light in the mail yesterday.

SMD 2835 Fitolamp 4000W 5000W LED Plant Light Full Spectrum Panel LED Phyto Lamp AC 220V Indoor Greenhouse Growing Bulb EU Plug|Growing Lamps| - AliExpress @ $42

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4000W 5000W LED Plant Full Spectrum

power draw 40-50w ROFL :rofl: :stuck_out_tongue_closed_eyes: :roll_eyes:

The lamp might work fine. But from a physics/science point of view, they lying, they lying hard.


maybe there going for wattage equivalent. What I do know is I have two modes with 216Leds 312Leds respectively for under $50

COB are just a single package that has dozens or hundreds of LED chips they were popular in the grow light community a few years ago but have been replaced by custom board type (sometimes called quantum boards) lights that have individual LEDs on them.

I really don’t like COB lights because they provide a single point source of light which everything tries to grow towards. Panel and board type lights are a bit better in this regard.

@lordkiwi if you have a Lux meter can you take a measurement at 3’ away from the light