What Watt Light Bulb is Needed For Growing Weed?

Of all the factors it takes to grow a successful cannabis plant, lighting is definitely the most important one.

After all, light is your plant’s food.

If you don’t feed your plants the right food, they’re not going to produce the big potent buds you’re looking for.

Today we’re going to talk about what watt light bulb is needed for growing weed.

We’ll also discuss some other things that you should watch out for when choosing a grow light for your setup.

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What Are Watts?

Wattage is a measure of the electrical power a grow light uses.

When talking about wattage, there are two key measurements:

1. The amount of electricity the light consumes (which impacts your electrical bill)
2. The amount of electricity the light outputs (which is an indication of its power).

TIP: Using an LED grow light will output a high number of watts while consuming relatively few, meaning big yields and low electricity bills.

Higher Wattage = More Weed

Generally speaking,  the higher the wattage of the grow light you use, the more weed your plant will produce.

For example, If you’re growing a single plant, a 1000 watt grow light will produce a larger yield than a 300w watt light.

However, how do you know the exact wattage of light you require?

How To Calculate The Wattage Of Light You Require

The wattage of light that you require for growing weed depends on two things:

1. How many plants you are growing- Each cannabis plant requires at least 1 square foot of space to grow in. This allows the plant room to grow to its full potential without being impeded by the plants around it.

2. The size of your grow space – For LED and HID grow lights, the minimum recommended wattage per square ft of space is 50w. It jumps to 150w for fluorescent lights.

Therefore, to calculate the wattage you require, you need to calculate the square foot of your grow space and multiply it by 50 ( the minimum recommended wattage per 1sq ft of grow space )

Example: My grow space is 2ft long and 3ft wide. Multiplying the length and width gives me  6 ( the square feet of my grow space ) I would then multiply this number by 50w to get 300w. Therefore, the minimum wattage I require for my grow space is 300w.

The following table shows how the wattage required increases with the size of your grow space.

Grow space size Minimum wattage required ( HID & LED )
1ft x 2ft 100w
2ft x 3ft 300w
3ft x 4ft 600w
4ft x 5ft 1000w

You’ll also have to take note of what type of bulb you’re using, because cfl bulbs for growing weed will be slightly different.  Although wattage is an important consideration when growing weed, there is another measurement you should understand before choosing your grow light…

PAR Output

PAR, which stands for Photosynthetic Active Radiation, is a scientific term for the light wavelengths that your plant actually uses to grow (photosynthesis)

Where wattage tells us how strong the light is, PAR gives us an accurate measure of how much edible light your plant is getting.

Therefore, when looking for a grow light, it’s much more important to know the PAR value than wattage.

Plants need higher PAR values as they mature.

A seedling will thrive under a lower PAR value between 200 and 400.

Established plants that are still vegging will do best under a 400-600 PAR light.

Flowering plants should receive a minimum of 600 PAR.

In general, lights with higher wattage should have a higher PAR output.

Most good grow light manufacturers will provide information on PAR output.

Any company that cannot provide this information should be avoided, since it’s unlikely they’ve done the testing required to ensure the light will work for growing cannabis.

However, If you’re browsing a light that doesn’t provide this information, feel free to reach out to the manufacturer.

Which Grow Light Should You Get?

So which grow light should you go for?

If you’re growing indoors, then you should opt for an LED grow light.

They’re efficient, reliable, run cool, and have very effective spectrums.

If I’m growing between 1-4 plants, I use a 600w grow light.

If I’m growing any more than 4 plants, I’ll hang two side by side.

Check out the table below to compare my 3 favourite 600w LED grow lights:

If you’re still wondering what grow light you should get, take a look at my recently updated guide to the best LED grow lights:

[amazon table=”6590″]

Final Thoughts

Although wattage is an important factor in deciding what grow light to purchase for your weed, it’s important to consider the PAR output too.

The best grow lights combine high wattage, lumens, and PAR  with a full spectrum of light wavelengths to maximize your yield.

I hope you found this article useful, please let us know if you have any questions in the comments below!

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James Alexander James Alexander
Hey, I’m James! The founder and head writer here at GreenBudGuru.com. I started this site to share my passion and knowledge of all things cannabis. I used to work as a budtender in central Amsterdam, and have over 7 years of growing experience.

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