How many Plants can I Grow with a 300w LED Light?

(Last Updated On: October 10, 2021)

How many Plants can I Grow with a 300w LED Light?

LED lights are the go-to choice if you are planning to grow plants indoors. They might be a bit expensive but more than makes up for it in the long run. LED lights have a cooler heat signature, saves energy and lasts longer.

How many Plants can I Grow with a 300w LED Light

The lights are the most important equipment in your growing room. You need to find the right type and right-sized light for getting the best results. So, many people ask the question- how many plants can I grow with a 300w LED light? 

Well, there is no direct answer to that question. It depends on many things. Keep on reading to find out more about this!

What size LED grow light do I need?

Don’t make up your mind about getting a specific sized LED light. A 300W light may or may not be enough for you. It boils down to how much space you have available, how many plants you want to grow, which technique you want to use.

You can plant 1-3 plants per square foot depending on the method you use. We’ll walk you through the methods in detail shortly. 

Let’s assume you want to grow weed. You will need around 33 actual wattages of light for a weed plant per sq. ft. That means you can cover an area of (300/33)= 9 sq. ft. (approx.). The grow room/ tent has to be 3×3.

So, if you have a 3×3 grow room, you will need 300 watts of actual light. Keep in mind a 300W light does not yield 300 watts of power. A high-quality light may get close in output but the average ones don’t even come close!

How many plants can I grow with a 300W LED light?

According to our calculation, let’s say you have a 3×3 grow room and need a 300W LED light to cover that. So how many plants can you grow under 300w ? Let’s talk about it.

A 3×3 grow room or tent can contain a decent number of plants. We’ll give you a good example here.

How many plants can I grow with a 300W LED light

You can have 9 plants within this area if you use the Sea of Green method. Applying the Screen of Green method, you will have 12 plants and the topping method will also let you grow 12 plants.

If you want to use the medium grow technique, you can have 2 plants. A low-stress training will let you have 4 plants.

Pro tip: You can have a rectangular grow tent/space where each plant gets a square growing space. This way, the plants will also get an even and well-distributed light spectrum. 

Indoor plant growing methods

Before preparing a growth environment, you need to decide on a growing method.  There are 5 common indoor growing methods. You need to decide how many plants you want to grow, how large you want them to be. Everyone has different tastes. Remember, each method has its pros and cons. Pick a growing method based on your needs.

The Sea of Green method

This is low-stress training and is ideal for small cannabis plants. If you can do it properly, you will get a high amount of yield. The Sea of Green method allows multiple harvests in a year. 

Sea of green technique

Compared to the Screen of Green method, you can get more plants and get the plants to harvest faster. You don’t need much vertical space in this method and works best for commercial-scale gardening. 

However, the plants are more vulnerable to pests and diseases. So, you have to be more careful regarding the health of your plants.

In the Sea of Green method, each plant needs at least 1 square foot of growing space.

The Screen of Green method

This method is used by employing a screen over the cannabis plants to track their growth. When the plants cross the screen, you need to prune them. The benefits of this method are an efficient use of the growing space, less power and nutrient cost and work well with seedlings and cuttings.

Screen of Green method

However, the grower needs to look after the plants meticulously. It requires some extra effort. You need to constantly track the growth of the plants and prune them when needed.


You need to prune the highest part of your plant in this method. It allows you to produce more buds by taking advantage of stress exposure. You can increase your yields without adding any enhancers using this method.

Topping technique

The topping method lets you make the most out of your plant’s capacity. You can ensure your plants absorb light better by pruning the highest part of them. This technique is ideal for the mature stage of the plants.

If you want to apply topping to your cannabis, make sure you earmark around 0.75 square feet of space.

Low-stress training

Low-stress training takes full advantage of your growing space while keeping a uniform height. When cannabis starts growing into a conical shape, this method alters the direction into a horizontal space and keeps the height uniform.

The advantage of this method is it ensures efficient light distribution and equal growth of the plants. More light gives the plants more nutrition and improves the quality of the buds.

It’s difficult to cultivate a large number of plants using this method. It’s best for people who are growing a limited number of plants non-commercially.

Applying this method makes the plants grow horizontally, so provide 2 square feet of space for each plant.

Medium-sized growth method

This is a straightforward method. It’s best for medium and large-sized plants. These plants need more space to branch out. Just give them the space. You don’t need to change the direction or anything. It’s relatively easy to maintain.

The recommended space for each plant in this method is 4 square feet.

300 watt led grow light power consumption

Many people will tell you LED grow lights barely use any power. The manufacturers exaggerate even more. Well, they certainly use power. Yes, they are efficient but they don’t run out of nothing!

If you have a big sized growing room, you are going to have quite a high electricity bill. So, what about the hype, then? Why are people talking about it? It’s because LED lights are excellent for the long run. They certainly cost less than other types of lights i.e., HID lights. So, let’s get over the confusion.

Do LED grow lights use a lot of electricity?

If you use big lights, it will naturally incur a high cost. But LED lights use less power compared to other types of lights with the same output. You will pay less to get the same output. 

Depending on the light size, you may get a high electricity bill but it will be less compared to the other ones. 

Chinese brands are notorious for providing false information sometimes. But most of the trustworthy manufacturers will tell you how much actual power the LEDlights will be able to draw. 

A good light should have a power drawing capability closer to the intended output. An average 300W LED light can draw only up to 120-150 watts of actual power, while a high-quality light can draw 180- 200 watts.

300w LED grow light calculator

Let’s be honest for a second. Setting up a growth environment for your plants will need some investment. You need lights, tents, a ventilation system and CO2. The cost of the other equipment is fixed. 

The majority of your electricity bill will come from running the lights. If you have a good idea about the electricity bill from running the lights, you can have some realistic expectations and prepare a growth environment accordingly. So, here we’re going to give you a grow light calculator formula. You can use that to make estimations.

First, you need to know how much it costs in your region per KWh. Depending on where you live, the costs may vary. In the US, Hawaii has the highest average electric rate- 30.55 cents/kWh. On the other hand,  Oklahoma has the lowest average electric rate- 8.92 cents/kWh.

For reference, let’s say you’re from Utah and it costs around 10.04 cents per kWh there. If you need to know the average electric rate in your state, see here. You will get information about all the states within the US from here.

Now, let’s put the information in a box and calculate the approximate cost. Let’s assume you’ll use a 300W light for 16 hours.

Watts per hour (this refers to the light size)Electricity bill(per KWh)Light running time(hours)

Here’s the formula. We need to calculate the KWH first.

KWh=  Number of appliances x Power rating (watts) x Usage (hours)

Your usage = (1 light x  300 watts x  16 hours ) ➗ 1000

                      = 4.8 kWh

Average per KWh cost is $0.10 (10 cents) 

Your approximate bill for a day=(4.8 x 0.10)

                                                          = $0.48

                                                          = 48 cents

Approximate bill for a month = (0.48 x 30)

                                                      = $ 14.40 

Approximate bill for a year = (14.40 x 12)

                                                  = $ 172.8

How many hours a day are needed for indoor plant grow lights?

If your plants don’t get optimal lighting, they will not grow like you want them to. The plants will need more time in artificial light if they don’t receive any sunlight. So, if you don’t have a window that lets sunlight into all the plants, you need to make sure they get even lighting for a long time throughout the day.

Seedlings and high-light plants

Seedlings require high-intensity light to grow properly. You should use reflectors to make sure the plants get even lighting and maximum intensity throughout the day. The reflectors will shed the light onto the top and sides of the plant properly. 

Seedlings and high-light plants

A seedling requires around 16-18 hours of artificial light if they don’t get any sunlight throughout the day.

Low and medium-light plants

Most of the houseplants will grow well in 12-14 hours of artificial light without any sunlight. The medium-light plants require about 6 hours of artificial light per day with sunlight in the daytime for 2-3 hours. If they don’t get any sunlight at all, provide an additional 3-6 hours of artificial light. African violet, Begonia, Bird’s nest fern are some of the popular medium-light indoor plants.

Low and medium-light plants

Low-light plants grow well with around 4 hours of sunlight daily. If you can’t manage access to sunlight, give them around 6-8 hours of artificial light. Ivy, ZZ plant, Snake plant, Staghorn fern are some of the best low light plants that you can grow indoors.

It’s difficult to get the ideal to grow light for fulfilling your yield expectations.

300w LED grow light yield

It’s difficult to get the ideal growing light for fulfilling your yield expectations. It gets more difficult when you have a small grow space to work with. You need to make the right calculation and adjust your gardening efforts accordingly. Don’t worry. We’re here to make things easier for you.

A 300W LED light is ideal for 1-6 plants. If you want to get the best yield, a maximum of 2-4 plants is recommended. If you go beyond that, you will not get a good yield.

If you use soil to grow, you can expect 20%-25% less yield compared to a hydroponic setup. The lights are the food to your plants. It turns into energy during the photosynthesis process and fuels the vegetative and blooming phase of your plants.

Your plants will give you better yields when they get maximum light intensity. Yields are connected to the genetics and strain of the plant as well. You should use the same light throughout the plant’s life. Light changes during the vegetative and blooming stage will shock your plant and stunt its growth and development.

The light intensity and full spectrum of the lights are the most important things. A single light will save your money and effort. However, if you are gardening for yield, keep in mind that usually a 300W LED light can draw only about 120-150 watts of power. The number of LEDpanels doesn’t matter. Don’t be fooled by that.

In order to be sure about your yield, figure out how much power the light can actually draw. It will help you make some realistic expectations.

Best 300w LED Grow Light

Like we have mentioned so many times in this article, light is the most important component in your grow room setup. Here we have rounded up some features of the best LED lights. When you’re buying lights, check and make sure they have these features.


The higher power a LED grow light has, the more area it will cover. Try to get lights that can draw power close to the stated wattage. For example, you have two options. A 300W light can draw about 140 watts of actual power and there is another one that can draw up to 170 watts of power. Buy the one that can draw 170 watts of power. 


We will not bore you with too much science here. Plants need red and blue lights for photosynthesis. Lights with a higher PAR rating provide a high amount of these wavelengths. Simply put, a higher PAR rating means a more effective grow light.


Just like with PAR, a higher PPFD rating indicates a more effective light. We are not going into the details of these terms because these things are a bit complicated but if you want to learn, you can check out this.

Height and area

Grow lights produce the best results when hung from a specific height and used for a specific area. For example, a 3X3 grow space can be covered with a 300W LED light hung from 24” above. Make sure the light you pick meets these requirements.


The spectrum of the lights is important. It refers to the wavelengths a light can produce. Most grow lights are sold as full-spectrum lights but not all of them contain infrared and UV rays. UV light can prevent bacterial infection. So, consider buying lights that can produce infrared and UV rays.

Different modes for different phases

Some lights come with different modes for different phases. A full-spectrum light will produce all the wavelengths all the time. But if you can find a light that can be switched for the vegetative and blooming stage, get it. Because it’s more effective and will help your plants grow better.

Safety feature

LED lights run cooler than most other lights. But if they run for a long time they also need to be cooled down to prevent overheating. The cooling system comes with one or more fans and a heat sink to prevent overheating. Some LED lights operate separately so when a light is burnt it does not burn the whole unit.

300 watt LED grow light distance from the plant

How far your light should be placed depends on the power and intensity of the light. The light should be placed at different distances during different developmental phases of the plant. Typically, a 300W LED light should be placed 12-30 inches away from the tops of your plants. Let’s dive into the details.

300 watt LED grow light distance from the plant
  • Seedlings need to be kept the furthest away from a 300W LED light to prevent the roots from drying out. Place the light 24-30 inches away from seedlings.
  • During the vegetative stage, the demand for high-intensity light increases. Bring the light closer to the plants. Place the light within 12-18 inches away from the top of your plants.
  • During the flowering/blooming stage, plants require less high-intensity light. Take the lights a bit further away during this phase. Ideally, put the light 18-24 inches away from your plants.

People also ask

What is a 300 watt LED grow light equivalent to?

This varies from brand to brand. For example, Advanced Platinum P300 is one of the most highly rated LED grow lights. It is equivalent to a 300W HID light and can draw almost 300 watts of power! On the other hand, Meizhi 300 LED horticultural light is equivalent to a 200W HD light and can draw merely around 130 watts of actual power.

How much does it cost to run a 300W LED grow light?

It depends on where you live. In the US, Oklahoma, Oregon and Utah have some of the lowest average electricity rates. On the other hand, Hawaii and Rhode Island have the highest average electricity rate. 

According to our calculation in this article, a 300W LED light may cost you around $173 for a month in Utah. It will cost you at least thrice the amount in Hawaii and Rhode Island.

How much area does a 300 watt LED grow light cover?

We recommend using a 300W led grow light in a 3X3 grow space. It is ideal for that space. If you go beyond that, you may not get the best results.

How many 300w led lights do I need for 12 plants?

Again, the answer to this question depends on various things. The first thing to consider is how big you want your plants to be. A single 300W led grow light is enough for growing 12 lights using the Sea of Green method. If you want your plants to be medium-large in size, you will need 6X300W lights for 12 plants.


Grow lights are the most important element in your grow room. If you want the best results, invest a bit of money initially. It will be worth it in the long run. Depending on the method you use, you can grow 1-12 plants with a 300W led light. Before buying a light, think about the cost, the space you have, how big you want your plants to be and how much yield you expect from your plants.

Hope you enjoyed reading this. If you want to learn more or have any questions, feel free to let us know.

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