What Size Grow Light Do I Need? | Major Factors to Consider When Growing Pot Indoors

by Morgan

May 1, 2022

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As you probably know, grow lights are essential for indoor gardening. They provide the light that plants need to grow, and without them, your plants would not be able to thrive. But what you may not know is that there is no one-size-fits-all answer when it comes to growing lights. The size of the grow light you need will depend on several factors, including the type of plants you are growing, the size of the growing area, and the amount of light the plants need.

There are a few different types of grow lights available on the market, and each has its advantages and disadvantages. Keep reading as we break down everything you need to know about choosing the right grow light for your needs.

Major Factors That Will Determine the Size of Grow Light You Install

Type of Plants

The type of plants you are growing will play a significant role in determining the size of grow light you need. Some plants, such as succulents, do not require a lot of light and can even do well with artificial light that is not as bright as sunlight. Other plants, such as tomatoes, need a lot of light to produce fruit, requiring a bigger and more powerful grow light. A single weed plant will require around 40-60 watts per square foot.

Size of the Growing Area

The amount of the grow light you require will be determined by the size of your grow room. If you have a large growing area, a larger light is ideal for covering the entire region. If you have limited growing space, on the other hand, you can get away with lesser light. It's worth noting that the height of your grow room will influence the amount of light you'll need. Taller grow areas will necessitate taller lights to ensure that all plants are illuminated.

For example, a decent rule of thumb for LED grow lights for flowering medicinal or other large flowering plants is 32 watts of actual light coverage per square foot of growing space. As a result, a 33-foot grow area would require at least 288 watts of real LED power.

Number of Plants

The number of plants you are growing will also play a role in determining the size of grow light you need. If you only grow a few plants, you can get away with a smaller light. However, if you are growing many plants, you will need a bigger and more powerful grow light to ensure that all of your plants get the light they need.

Light Requirements for the Plants

Different plants have different light requirements. Some plants need full-spectrum light, while others do better with just blue or red light. Before choosing a grow light, research the specific light conditions of the plants you want to grow to ensure you get the correct ones for your plants.

Amount of Light Needed

The amount of light your plants require will also influence the size of the lamp you require. Some types of plants require more light than others, so you'll need a more powerful grow light if you're growing a plant that requires a lot of it. Conversely, if you're growing a plant that doesn't require as much light, you can use a lower-powered light.

a person in the indoor garden

Types of LED Grow Lights and Their Sizes

Now that we have covered the major factors that will affect the size of grow light you need, let's look at the different types of LED lighting available on the market and their sizes.

Compact Fluorescent Lights (CFLs)

Because they are compact, economical, and simple to set up, CFLs are one of the most popular grow lights. CFLs come in various sizes, but the 23-watt bulb, which is equivalent to a 100-watt incandescent light, is the most prevalent. You'll need at least 32 watts per square foot for a four-by-four-foot area.

High-Intensity Discharge (HID) Lights

These are more powerful than CFLs and are typically used by experienced growers. The most common type of HID light is the metal halide (MH) light, which emits intense blue light, and the high-pressure sodium (HPS) light, which emits red light. MH and HPS lights come in various sizes, but the most common sizes are 1000 watts and 400 watts. For a small space measuring four by 4, you will need at least 600 watts.

Light Emitting Diode (LED) Lights

An LED light is the newest type of grow light on the market and has become increasingly popular among growers. LEDs are more efficient than CFLs and HIDs and produce very little heat, which is ideal for small grow spaces. LED lights come in various sizes, but 50 watts, 100 watts, and 200 watts are the most common sizes. For a small room measuring four by four, you will need 400 watts.

Fluorescent Tube Lights

Fluorescent tube lights are not as popular as they were, but they are still a good option for growers who want inexpensive, easy-to-use grow light. Fluorescent tube lights come in various sizes, but the most common length is the T5 light, which is 5 feet long. A single T5 light is equivalent to actual wattage of 40 CFL. You will need at least 32 watts per square foot for a small space measuring four by.

Induction Lights

Induction lights are a newer light that is becoming increasingly popular among growers. Induction lights are more efficient than HIDs and emit very little heat, which is ideal for small grow spaces. Induction lights come in various sizes, but the most common length is the 400-watt light. For a small room measuring four by four, you will need at least 600 watts.

What Is the Correct Grow Light Size for Plants Growing in Tents, Greenhouses, and Other Large Spaces?

The size of the grow light you need will also depend on the size of the space you are growing in and how many plants you are growing. You can get away with a smaller light if you grow your plants in a small area, such as a closet or cabinet. However, if you grow in ample space, such as a tent or greenhouse, you will need a bigger and more powerful light to ensure that your plants get the light.

  • For a small tent measuring four by four, you will need at least 32 watts per square foot.
  • For a large tent measuring ten by 10, you will need 400 watts
  • You will need at least 32 watts per square foot for a small greenhouse measuring four by four
  • For a large greenhouse measuring ten by ten, you will need at least 600 watts

FAQs

What Size LED Grow Light Do My Plants Need?

The size will depend on the factors we discussed earlier, such as the size of the grow space, the type of plants you are growing, and the amount of light your plants need.

How Many Watts Do I Need Per Square Foot?

The number of watts you need per square foot will depend on the factors we discussed earlier, such as the size of the grow room, the type of plants you are growing, and the amount of light your plants need. However, a general rule of thumb is to use 32 watts per square foot for small spaces, 100 watts per square foot for medium areas, and 200 watts per square foot for large rooms.

How Big Should My Grow Light Be?

The size of your grow light will depend on the factors such as the area your plants are covering, the type of plants you are growing, and the amount of light your plants need. Too much light or too little will be harmful to the plants. However, a general rule of thumb is to use a grow light of at least 50 watts for small spaces, 100 watts for medium rooms, and 200 watts for large areas.

What Size Grow Light Do I Need for A 4x4 Grow Tent?

For a small space measuring 4 by 4, you will need at least 32 watts per square foot. However, a general rule of thumb is to use a grow light of at least 50 watts for small spaces, 100 watts for medium areas, and 200 watts for large rooms.

What Size HID Light Do I Need?

The HID light you need will depend on the factors we discussed earlier, such as the grow area size, the type of plants you are growing, and the amount of light your plants need. However, a general rule of thumb is to use a metal halide (MH) light for vegetative growth and high-pressure sodium (HPS) light for flowering. MH lights range from 175 watts to 1,000 watts, while HPS lights come in sizes ranging from 150 watts to 2,000 watts.

What Is the Best Grow Light?

The best growing light is the one that best meets your needs. There are various grow lights on the market, so choosing the right one for you is essential. Factors to consider are the type of plants you are growing, the grow room dimensions, and the amount of light your plants need.

Cannabis plant

Final Thought

Now that you know the significant factors that will affect the size of grow light you need, you can decide which light is right for you. If you are still unsure about which light to choose, we recommend talking to a knowledgeable grower or contacting a grow light company for more information.

No matter what type of grow light you choose, follow the manufacturer's instructions carefully to ensure that your plants get the light they need to thrive. At 420 Green Thumb, we also have a wide array of information on grow lights, so feel free to browse our site for more tips and advice.

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About the author 

Morgan

I discovered the benefits of Cannabis at a young age in 2002, with years of trial and error, my knowledge grew just like my plants. As my love for cannabis unfolded I began to teach and learn, trying to gain as much information and practical growing experience.

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