LED Grow Lights Coverage   Over the last few months, it has become blatantly clear that the primary reason people are purchasing LED Grow Lights is NOT to grow tomatoes and herbs. While I am sure there are a select few visitors that do actually grow everyday food or herbs indoors and even fewer still that inquire about outfitting a greenhouse for any number of plants, a majority of site visitors are here for one reason: using LED Grow Lights to grow cannabis.

Dear Feds,

Neither myself or this website condones or supports any illegal activities. Information is provided for legal medical cannabis growing operations and educational purposes in the event laws change. All readers are expected to check with local laws before growing.

   With that out of the way, it is safe to say that most of this site’s visitors that purchase LED grow lights are doing so with the sole purpose of growing cannabis for personal/medical use. I know this and, most importantly, other LED Grow Lights manufacturers know this as well so why do most of the published coverage areas seem out of touch with reality?

LED Grow Light Coverage

   While some grow light companies flat out overstate their recommended growing area simply to dazzle the visitor into purchasing, others have not-so-sinister reasons for their claims. The former is out to make a quick buck – customers be damned – and they end up shooting the industry in the foot by perpetuating negative reviews. This is especially true of low-wattage LED panels and spotlights. The latter is trying (sometimes to the detriment of its bottom line) to keep neutral by not catering to any particular customer niche, i.e. Cannabis Growers.

   Coverage area varies widely depending upon many factors:

  • manufacturer
  • wattage of individual diodes
  • shape of the grow light
  • degree angle of the diodes
  • overall wattage of the light
  • intended usage
  • . . . the list goes on

   Of all of the reasons coverage is affected, the most important is its intended usage. You see, many manufacturers publish coverage areas based on the vegetative stage. This is a very important point. When plants are in the vegetative stage, they need less intense lighting than in the flowering stage. As cannabis growers already know, getting plants successfully through the vegetative stage with LED Grow Lights is pretty straight forward at this point. It gets tricky when bringing your plants through the flowering stage successfully due partly to the fact that some lights are just not up to the challenge. More importantly manufacturers are eager to show clients a huge savings in electricity (thus justifying the higher entry cost) stating a 100W LED grow light can support a gardening space of 3’x3′.

   Let me be blunt here – a 100W LED grow light CAN support a 3’x3′ footprint but only during the vegetative growth of plants like lettuce, herbs, and some fruits and vegetables. If that is what you are wanting to grow then you will do just fine. For those of you growing cannabis, coverage expectations need to be put in check.
Loose Cannabis Bud

Big Grow Space – Little Light, A Recipe For Disaster

   A common complaint about LED Grow Lights among cannabis growers is that they just don’t get the yield they were expecting as compared to their previous grows using HID lights. Or things might look great when growing – big leaves, tons of buds – but comes up short on dry weight due to light, airy buds instead of the thick, dense buds they may be used to.

   If your buds are looking like the wispy little nug on the right, then your issue could be that you are trying to grow more than your light can handle. Trying to force that 100W LED grow light to fully flower all your plants in a 3’x3′ space is never going to work.

   What you need to do is reduce the coverage area – generally by 30-50% – of what a manufacturer states the light can handle for the common gardener growing flowers or herbs for cooking – i.e. vegetative growth. So now you can use that 100W LED grow light in a 2’x2′ space (enough for a couple decent plants or even a SOG/SCROG) and come away with thick, dense bud as you see in the picture below on the left.Dense Cannabis Buds

LED Grow Light Coverage Area Guide

   I have already stated that there are many factors that can affect the coverage area of LED Grow Lights, here is a rough guide to what I think are suitable grow spaces for a given wattage of light. By keeping these guidelines in mind with your growing effort, you will find that your results will match or exceed your expectations.

Light Wattage Vegetative Stage Coverage Flowering Stage Coverage
100 Watt 2.5′ by 2.5′ 2′ by 2′
150 Watt 2.5′ by 3.5′ 2′ by 3′
225 Watt 3.5′ by 3.5′ 3′ by 3′
440 Watt 4′ by 4′ 3′ by 3′
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8 Responses to The Cannabis Grower’s Guide To LED Grow Light Coverage

  1. David says:

    The whole process of cannabis cultivation is definitely a good thing when you are striving for healthy stamens pistils and cloudy trichomes. The articles Mathew has attributed the growth with led is fascinating. Good luck always David

  2. Sally Skimin says:

    Just a quick question. When you’re talking watts for coverage area and I was to use cree cobs 3070 rated around 117 watts per chip would I factor in the wattage from the manufacturer or the percentage it’s being driven at which would be 60%. I have 8 cobs and want to cover a 4′ x 5′ area.

    • Mathew says:

      Hi Sally –

      You would rate it on actual power delivered…in this case its 117w x 0.6 = 70.2w per COB… x 8 = 561.6w total / 20 sq ft = 28.8w per sq ft.

      This is on the low side of what I would recommend for your grow space but it would depend on the quality of the light and the spectra emitted.

      We have an Alaska distributor if you need someone local…just let me know and I can put you in contact with him.


      • tim says:

        I have a 4’x4’x7′ tent will this light be awesome or no ?
        King Plus 800w Double Chips LED Grow Light Full Spectrum for Greenhouse and Indoor Plant Flowering Growing (10w Leds)

        • Mathew says:

          Hi Tim –

          No doubt you are drawn to that light because of its high wattage and low cost…but here are the facts:

          It is based off of 80 x “10w” chips but they are not really 10w…they are 2x5w chips. All they are doing is putting two chips per diode instead of using a real 10w diode. This WILL lead to heat issues. I have been in this industry for 7 years now and this is exactly what they used to do for 3w diodes…they would use 3x1w chips in the same diode.

          The actual power output is 180-220 watts – not the 800w you are expecting (just read the full description of the light on Amazon). There is no light on the planet, no matter what brand, that will cover 4×4′ with 200 watts. This is at best coverage for 2’x2’…so you would need four of them for your tent.

          Bottom line is that this light is nothing like what they advertise and will fail prematurely because of how it is built.

          Sorry for the bad news but if you would like to talk about what we can offer – just give me a call.


  3. carole says:

    I have a 32x32x63 grow tent. My first ever. I want to use four 75 eq daylight led bulbs in a four splitter to give me 300 eq watts in each of two splitters for a total of 600 eq watts to grow 3 plants. Is this too much light?

    • Mathew says:

      Hi Carole –

      Of course I would recommend using something like our TL440 in this setup – it would give better results.

      However, can you tell me the actual power draw of the bulbs you are talking about – not equivalent?


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