Last Updated February 5th, 2023: There are many factors that go into growing a successful cannabis plant. But without light, your plants won’t make the potent buds you’re looking for. That is why it’s important to know how much wattage of grow lights to use in order to have healthy and thriving plants.
Here we’ll talk about what wattages of bulb work best when trying out different strains with low-stress training techniques as well as some other things one should be careful not overlooks while selecting lighting fixtures for their setups such as heat production or electricity usage.
What Watt Light Bulb To Use For Growing Weed:
At a minimum I would recommend at least a 150 watt LED light bulb for growing weed. That being said, that’s pretty much the minimum for a small single cannabis plant during the initial stages of growth. Once the plant grows and reaches flowering, you’ll need more watts because the plant needs more energy, but also because the plant will be bigger and wider and will require light across more space. Below is a table based on growing size, and the minimum wattage required for these situations.
Cannabis LED Wattage Table:
| Size of Growing Space | Minimum LED Wattage Required |
| 1 foot by 2 feet | 150w |
| 2 feet by 3 feet | 300w |
| 3 feet by 4 feet | 600w |
| 4 feet by 5 feet | 1000w |
How To Calculate How Much Wattage You Need For Your Grow:
The wattage of light you need to grow weed depends on two things: how many plants are in the space and what type of lights you’re using.
For a typical cannabis plant, they require one square foot at minimum to thrive properly without being hindered by surrounding plants or other obstacles. For a traditional LED grow, it needs 150 watts per sq ft while fluorescents would only need 50 watts per sq ft.
So from there, you would just take your Square Footage x 150 watts (LED) or 150 watts (Fluorescent). Along with this, this can fluctuate slightly depending on the individual type of bulb you’re using, but they’ll generally provide you with their recommendations.
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).
Using PAR values instead of wattage lets you find out how much consumable light your plants are getting. This makes it more important when looking at lights not just to know their wattages but also what type and strength of wavelength they emit in order to make sure there’s enough available food energy. Having higher PAR output can even speed up the grow time and give you an earlier finishing grow.
Seedlings will thrive with lower PAR around 200-400 while established vegging plants need 400-600 depending on maturity level: young plants can do well under 600 whereas mature ones usually require 800.
If a plant is flowering, then it should definitely have 600+ PAR to help provide adequate energy to the plants.
When you’re purchasing your grow lights, the manufacturer should provide the PAR Output of the lights, if they don’t provide them, then it means they aren’t a legitimate lighting provider.
What Even Are Watts?:
Wattage is the official measurement of the electrical power a lighting unit consumes or uses.
Watts are broken down by how much electricity your lighting consumes (AKA how much you pay for your electric bill) and the amount of light your lighting outputs (The overall power of the light bulb).
When you’re using lights to grow weed like in an indoor weed grow or especially a closet weed grow, then having more wattage will generally mean more growing power and could lead to a higher-yielding indoor grow.
Final Thoughts On Picking Wattages For Growing Weed:
When you’re looking for a grow light, it’s easiest to use the watts as a metric to help judge if the grow light will be sufficient for your growth.
Along with this, you can also use the PAR Output to help give you an additional metric to judge on if your plants will receive enough energy from the lights. Overall it’s better to focus on a slightly more powerful light rather than on the weaker end.
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