September 8, 2014

How Many LED Watts Are Required Per Square Foot of Grow Space?

The Ultimate Guide to Help You Choose the Correct LED Wattage for Your Grow Space (during flowering)

Are you new to the world of LED growing? If so, the charts below will help you determine how much energy (by wattage) your plants require for flowering.

Disclaimer: Wattage is a relic of the HID (MH and HPS) days. Wattage should not be used to determine the coverage area a fixture or the usefulness of an LED grow light. Wattage should only be used as a simple method for approximating the correct fixture size for your grow.

PPFD (umol/j/m2) and DLI is the correct metric for measuring useful light intensity over a given area. Coupled with the correct spectrum for your plant type and phase of growth, PPFD (and spectrum) are the keys to a successful grow. However, for the purpose of estimation, we will report wattage calculations in this article.

>>> GET A FREE BUYER'S GUIDE CHECKLIST <<<

Grow variables

It is important to understand that the number of actual watts that you need for your grow will vary depending on:

Plant type (high light or low light)

High light plants - i.e. tomatoes, peppers, etc
Low light plants - i.e. herbs and leafy greens (such as basil lettuce)

Growth phase

Seedlings, vegetative, and flowering plants all require a different amount of light

Total area of your grow

A larger grow area will require more power

Watts per square foot

The average LED grow light draws about 40 watts to cover 1 sq ft for flowering. HID lights draw about 62.5 watts per sq ft. The energy saving that growers can expect from using LED grow lights instead of HID is around 38%. This energy savings only takes into account to savings growers gain when using LEDs fixtures. It does not account for other environmental factors where growers can save energy. For example, less ventilation and air conditioning may be used, or foregone completely, depending on the size of the setup and ambient temperatures. Total power savings may rise above 50% in certain scenarios.)

Different LED grow lights will have different efficiencies. More efficient LED grow lights will use fewer watts to emit the same amount of light that a less efficient LED grow light will emit. Therefore, wattage is not the most accurate tool to know how powerful of a grow light you need for a particular coverage area.

LED Wattage Chart Explanation

The wattages listed below assume you are flowering your plants. If vegging, you might consider reducing your wattage by 50% since vegging plants only require about half the light intensity. As always, it is best practice to follow the manufacturer's recommendations.

Using the charts

In each chart you will find the following columns:

'# of Plants' to be grown
Square footage that the respective number of plants cover
Recommended LED wattage for the number of plants grown in the respective space

Wattage charts

Assume about 32 watts/sq ft (actual LED wattage) for flowering. Fewer watts might equate to smaller yields while more wattage may lead to larger yields.

Quick Guide (watts per coverage area)

1' x 1': 40 watts

2' x 2': 160 watts

2' x 4': 320 watts

3' x 3': 360 watts

4' x 4': 640 watts

5' x 5': 1000 watts

4' x 8': 1280 watts

6' x 6': 1440 watts

Recommended wattage assuming 1.0 sq ft/plant

# of Plants	Square Feet	Wattage from Wall
1	1	40 watts
2	2	80 watts
4	4	160 watts
6	6	240 watts
8	8	320 watts
10	10	400 watts

Recommended wattage assuming 2.0 sq ft/plant

# of Plants	Square Feet	Wattage from Wall
1	2	80 watts
2	4	160 watts
4	8	320 watts
6	12	480 watts
8	16	640 watts
10	20	800 watts

Recommended assuming 4.0 sq ft/plant

# of Plants	Square Feet	Wattage from Wall
1	4	160 watts
2	8	320 watts
4	16	640 watts
6	24	960 watts
8	32	1280 watts
10	40	1600 watts

Shop LED Grow Lights ›

Related: Best LED Grow Lights 2022

Notes: Please be aware that the cultivation of certain plants may or may not be legal within your own specific region or country. LED Grow Lights Depot does not encourage or condone any illegal activity and advises each individual / user to inform themselves of the relevant laws within their own region/country.

Previous article Best LED Grow Lights 2022 Video

Comments

Ozz - August 9, 2018
Well go to Walmart online and you can get a LEDs for 80 to a100 bucks. I got a 1200 watt light I use more white and blue,then I got 2 _ 600 watt LEDs to. if you buy to 600 watt lights ( more red) you can cover more area being they shine straight down. These lights use very little power to running so 2400 watts cost 200 buck and maybe run power bill up 10 bucks. Note that keeping the light around 18 inches above your plants because you can burn then! Also the higher to put it the less stretching on your plant which mean tighter Leaf space which equal more flowers.

Mark - July 8, 2018
40 yrs exp.and sometimes less is more .Seedling n young clones need less more difused light so just old shop lights to start then add in or change up to led or what ever.

John - January 1, 2018
What you have to remember, there is a direct relationship between true wattage and plant mass example it doesn’t matter what your growing, so if we say you have 4 plants and you are providing 600 watts of light and you get 40oz of dry plant matter, for ease of convenience you get 10oz per plant, so lets say now you add 4 more plants under the same wattage you will still get 40oz of dry plant matter it will be distributed amongst the 8 plants in the form of 5oz per plant, so if you want more plant mass (fruit) you have to feed them more wattage its that simple. Using LEDs always look at the true wattage drawn from mains, and not what the manufacturer claims is the wattage,

eh terry - December 7, 2017
Well it is almost 2018 and 100 bucks will get you the latest full spectrom 600 watt grow light.
But you could want to customize for your application.

The REAL ''The Dude'' - September 19, 2017
Ok this is pretty stupid. It’s 2017 now. It is VERY easy to get a GREAT LED customized to the spectrum YOU want. Go to amazon, you can buy a 600w LED for 100 bucks. You may say ‘’thats a cheap led’’. Ok, it has all the spectrums I ASKED THEM FOR and it has lasted me over a year. Do you think 100 bucks for an led that last for a year is more of a waste than a 400 dollar LED light that last 2 years?

LED lights have come a long way. They produce less heat, can be brought closer to the plants and cost less than HID. Penetration is no longer an issue because of these facts. You can bring the light very close to your plants without detrimental effect. A little training and your light easily reaches anywhere you want as long as its has the watts for it. If you know how to train correctly, you can get away with a lot less watts too but we’re not here for that.

All I’m saying is that you can get AMAZING results with a 100 dollar LED from amazon. There is no reason to buy anything else with the prices of these things now days. Go with what has the most reviews and make sure there is a return option.

LEDS

Cost less money to buy AND operate
Creates less heat
Can be brought lower to the plants without burning
Last longer than HID
Take up way less space
Can be customized to your specific light wavelength

james reeves - June 12, 2017
don’t waist money on expensive LED lights. i bought 150 watt LED “flood” lights at Lowes. they were $20 a pair. i purchased the metal round hangers where i inserted one bulb. i hung the lights on a rope 2 feet above the vegetative plants. the lights are about 2 feet apart on the rope. each came with a clip that can attach to rope. in an 8 foot area i have four 150 watt LED flood light hanging above the plants. the lights are on 24/7. my plants grow 3 inches every two days or about. The metal light fixtures cost about $6 at Lowes. two bulbs and two fixtures cost me about $52. plants grow very well.

Lostalot - March 17, 2017
So what’s better a 4ft by 8ft tent or a 6ft by 6ft tent and will a single 200 watt led light be sufficient for my tent

michel - March 11, 2017
Sorry to say but didnt see any useful info here
plants dont give a damn about lumens …they want umoles …in specific wavelenghts…
leds dont look as bright(flashy ?) as hps because there is no glare …from the bulb.
people get em too close and stunt or burn their plants …lack is the far far red spectrum(black body) which is heat…quartz halogen can compensate for that in moderation (bloom) and there is no correlation between ‘’ how many plants’’ and led wattage…stuff 50 clones in a 2×2 even with a 1000 true watts led and they will all fall short or die ..cos they know the spatial space they occupy, and overcrowding is not their forte…and lets be honest top bin leds are like gold to lighting companies they are even reserved in advance and its not for grow lights that you get on the internet …those high end leds get you to spend mostly on cooling..and efficient led drivers , the leds themselves are very rarely top bin , so to give a better bang for the buck they fine tune the surroundings…dont be fooled and build yourselves a light , make it adlustable to your own needs and genetics the price will be about the same…but the overall quality will be better good day

Johnb341 - January 22, 2017
I simply couldn’t depart your web site prior to suggesting that I actually loved the usual info a person supply for your guests? Is gonna be again continuously in order to check up on new posts. fgdgededdcgk

Andre - October 17, 2016
So if i grow 16 plants on 11 sq. What do i need in watts?