How Many Watts Per Square Foot For LED Grow Lights?

In recent years, indoor gardening has gained a lot of popularity. This concept was only read in books a few decades ago, and it had less practicality in real life.

But welcome to the future! Now you can start your own futuristic garden.

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But you have to remember, because light is a basic requirement for plant growth, having enough light in a grow room is crucial for optimal yields. LED grow lights are without a doubt the greatest artificial lights available; however, how do you figure out how many watts per square foot LED grow lights should have? This article covers everything you need to know about wattage requirements.

What is wattage?

A wattage is a unit used to measure the amount of power/ energy consumed to light a bulb. Most people mistake wattage for brightness. Wattage doesn’t measure brightness but there is a positive correlation between the number of watts and the brightness of the bulb measured in lumens.

Understanding PAR output

Artificial light should give varied light spectrums similar to that of the sun for maximum plant yields. As important as knowing how many watts per square foot LED grow lights are, understanding the notion of PAR output is crucial if you want to give your indoor plants the best light possible. So put your glasses on and let’s get plant-nerdy!

What is PAR? 

PAR stands for (Photosynthesis Active Ratio), which refers to the portion of the light spectrum that plants utilize for photosynthesis. The essence of light in plants is to carry out photosynthesis.

You can see how important light is to plants because this is the method by which they create their own sustenance.

Different light spectrums exist, but only a fraction of them is utilized for photosynthesis. When it comes to PAR, different artificial lights differ, however LED grow lights have the maximum PAR, which is the plant edible component of the light.

The table below shows the PAR Output requirements at various phases of development.

Stage of Growth

PAR Output







How Many Watts Per Square Foot for LED Grow Lights?

The number of watts per square foot LED lights required is determined by a number of factors. These are the variables:

  1. Type of Plants

When it comes to lighting requirements, different plants have different requirements. Some plants need more light, while others only need normal lighting. Plants with a canopy, in particular, require more light to penetrate beneath their canopy, and more light equals more watts.

Tomatoes, peppers, and cannabis are examples of plants that require a lot of light. Herbs, on the other hand, need a moderate amount of light.

It is critical to first assess the lighting requirements of the plants you intend to grow before deciding on the required wattage. Plants’ output is negatively affected by both insufficient and excessive light, so you must strike a balance.


  1. Growth Phase

Germination, vegetative, and flowering are the three stages of plant growth.

The illumination requirements fluctuate in each step, which explains why some of the best LED lights contain an adjustable button for each phase.

Plants require less light during germination and more light once they reach the vegetative phase. The primary high-light requirement for plats is flowering. For plants to blossom and generate large buds, they need a lot of light.

  1. Number of Plants

One thing should be certain no matter how much you desire to grow more plants in the grow tent: plants require breathing space and, depending on the type of plant, should be adequately spaced. Just imagine the plants have to do social distancing for their own safety, just like us.

When evaluating the amount of watts required per square foot, the number of plants in the growing area is also an important aspect that should never be overlooked. The more plants, the higher the wattage needed, and vice versa!

  1. Spectrum light

Light spectrums exist in the sun, although they are invisible to the naked eye. However, the complete spectrum of LED grow light full spectrum is visible to the naked eye. The red and blue spectrums, in particular, are highly recommended because they are known to promote blooming and vegetative growth.

  1. Light Reflectors

Most people have never heard of light reflectors, but that doesn’t mean they aren’t necessary. Reflectors are required for optimal light consumption. Reflectors, when used correctly, can minimize the amount of wattage per square foot required to maximize plant production.

What is the purpose of reflectors in a grow tent? Reflectors are essential because they focus and reflect light on the plants.

This is especially beneficial because most grow rooms have dark walls, and the last thing you want are walls that absorb light needed for the plants.

Calculating Wattage Requirement Per Square Foot for LED Grow Lights

LED grow lights feature the highest PAR and the longest lifespan of any artificial light. A typical LED light lasts 10,000 hours. To extend the life of the lights, several businesses turn them off while they are not in use.

Some lights will be labeled as 5 watts but only use 3 watts. However, since we’ll be highlighting the average demand per square foot, this shouldn’t be an issue when calculating how many watts per square foot of LED grow lights.

For a 10 square foot grow area, 400 watts is usually enough. LED grow lights require an average of 40-50 watts per square foot.

This isn’t the case with all LED grow lights, as some are more energy efficient and consume fewer watts for the same amount of light. The average standard is 40-50 watts.

The size of the LED grow light is also important; if it is large, it will cover a large area.

Because a smaller grow light bulb will only cover a small area, more watts will be required to illuminate a larger area. 

Quick table showing the usual wattage per coverage area

Grow Tent Size


1′ x 1′

30W – 42W

2′ x 1′

60W – 90W

2′ x 2′

120W – 150W

2′ x 3′

200W – 220W

3′ x 3′

25W – 300W

3′ x 4′

380W – 400W

4′ x 4′

500W – 600W

4′ x 5′

600W – 650W

5′ x 5′

750W – 800W

5′ x 6′

900W – 1000W

6′ x 6′

1100W – 1200W

6′ x 7′

1200W – 1500W

Photo by welcomia