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Indoor lights for Cannabis grow: LED vs Bulbs

For new growers it can be easy to get lost with the different light fixtures. How can you decide on the best one?
25 April 2022
10 min read
Indoor lights for Cannabis grow: LED vs Bulbs

  • 1. Hid light bulbs
  • 1. a. Cost
  • 1. b. Ballast
  • 1. c. Reflector hood
  • 1. d. Air cooling
  • 1. e. Light bulbs maintenance
  • 1. f. Temperature
  • 1. g. Spectrum
  • 2. Leds
  • 2. a. Cost
  • 2. b. Led maintenance
  • 2. c. Temperature
  • 2. d. Spectrum
  • 3. Leds vs bulbs
  • 4. In conclusion

The best light fixture is a long-running debate, light bulbs are usually cheaper but emit more heat and need more maintenance while LEDs are more expensive but produce less heat, making it easier to control the temperature in your growing tent and consume less electricity, saving you money.

To choose the best light fixture you have to know what suits you best. Choosing the best light fixture for your plants depends entirely on your setup and budget. If you’re starting now, have in mind that cannabis produces trichomes to protect from UV rays, so the more light you give them, the more trichomes it will produce, resulting in better and denser buds.

1. HID Light Bulbs

HID (High-Intensity Discharge) light bulbs are the “classic” grow light. They were the first type of light used for indoor grow and are still used up to this day. That’s because they are cheap compared to LEDs and their efficiency has been proved throughout the years since indoor growing first became a thing.


Indoor lights for Cannabis grow: MH vs HPS bulbs

Metal Halide and High Pressure Sodium are the most widely used light bulbs for cannabis indoor grow.

Light bulbs can be found essentially in two types: Metal Halide (MH) and High-Pressure Sodium (HPS), and even though they’re both essentially the same thing, they are used in different stages of the plant's life cycle.


Bulbs are relatively cheap, but you will need more equipment to make the most out of them, ending up costing about $100 or slightly more. The equipment you will need is:


You will need a ballast to regulate the amount of electricity the bulb consumes, this will consequently extend the lifetime of the bulb. Ballast sometimes can also be used as a dimmer, to control the light intensity your plants are getting.


A ballast is used to control the amount of electricity your bulb consumes and can also work as a dimmer.

Have in mind that light bulbs should not be dimmed down until they get at least 100 hours of use at 100% power, this way they can stabilize. Dimming them down can diminish efficiency and can also affect the spectrum.

Reflector Hood

A reflector hood will help you to direct all the light to your plants.


Indoor lights for Cannabis grow: Bulb Hood For Interior Cannabis Grow

Reflection hoods are used to redirect the light downwards, allowing you to use 100% of the light produced by your light bulbs.

If you weren’t using this, the light would spread all over the grow tent but by using the reflector, it will be directed downwards, avoiding the waste of precious light and the energy bills that go along with it.

Air Cooling

When growing a lot of plants, you will need more wattage. Common wattages for indoor HID grow bulbs are 400W, 600W, and 1000W. This can increase the temperature in your growing environment so the best way to prevent that is to add a small exhaust fan along with the reflector hood. The ducting, along with the exhaust fan, will suck all the hot air out providing a constant air exchange that will keep the temperature in your growing room from oscillating.


Indoor lights for Cannabis grow: Air Cooled Hood

Air cooling is essential when growing with light bulbs as this will ensure they don't increase the temperature in your growing tent.

Because it is a closed air exchange, the air coming out won't smell like cannabis. This saves you from having to run the air through a carbon filter. You can find closed reflector hoods that come already adapted, so it’s quite easy and it’s definitely worth it as the high temperature can cause stress. The two main types of closed hood reflectors are squared (as shown above) or tubed. The square design offers a better light spread in a more uniform pattern but they do come at a higher cost. The tube-like design (usually referred to as a “cool tube” still offers good light spread, but is more suited to smaller grow tents than large grow areas.

Light Bulbs Maintenance

Light bulbs don’t need much maintenance other than cleaning and eventually changing a burned-out light bulb. Changing the light bulbs is easy, just take the burned one out and install the new one, you don’t need to change the whole fixture, just the bulb. Now cleaning it will take a little bit more work. Because the exhaust fan is sucking out heat, it can bring dust inside your reflector hood so you will need to clean it at least twice a year (preferably after each harvest). 


Indoor lights for Cannabis grow: Reflector Hood

Because the exhaust can suck dust in, you will need to clean it at least twice a year.

Remember to unplug everything before cleaning and use a microfiber towel slightly damped in a 50/50 mix of water and isopropyl alcohol to clean it thoroughly. Also make sure the whole fixture, especially the bulb, is completely dry before plugging it in back again as bulbs can explode if they’re too hot and come in contact with water. If your bulb burns out in the middle of the night there you won’t be able to replace it until the morning, so it’s essential to have spare bulbs. The lack of light when your plants should be receiving light will cause them to stress out.


As said above, it is essential to cool down your light bulbs, they can actually emit a lot of heat (depending on the wattage) and could show signs of heat stress plants or even becoming hermaphrodites. This will also make it difficult to adjust and control your growing environment when you are using more than one bulb or bulbs with a high wattage. This is because the temperature will drastically drop when the lights are turned off and then suddenly rise when they are turned on. If you’re growing in a cold place, light bulbs can help you keep the temperature up.


Although there are different types of bulbs, growers mainly use Metal Halide and High-Pressure Sodium bulbs. Both of them are similar the difference is that they emit different light spectrums.


Indoor lights for Cannabis grow: Light Spectrum in Cannabis

Ideal light spectrums for each stage of cannabis growth.

While MH emits a blue spectrum, ideal for the vegetative stage of cannabis for inducing plant growth, HPS bulbs emit a red spectrum, perfect for the flowering stage. This means you will have to change light bulbs when transitioning from the vegetative phase to the flowering stage.

2. LEDs

Even though there have been LEDs in the market for quite a while now, they are still considered new and even not good as bulbs by a lot of growers. 


Indoor lights for Cannabis grow: LED Light Fixture 

Led light fixtures emit a very bright and distinct light color.

That being said, lately, there have been a lot of companies producing really good LED fixtures that can be as good as bulbs or even better, although they can cost up to 10x more than a complete light bulb fixture.


LEDs can be really expensive, most growers avoid them because of their high price point, some reaching up to $1000. Obviously, you will find cheaper ones but the general consensus is that if you’re considering buying a $100 LED, you will be better with a bulb fixture. The high price comes with a benefit though. LEDs consume up to 60% less energy and you will make your money back with time. Although this is maybe useless to people who grow for their own consumption as they won’t profit from their plants. There are growers that make their own LEDs, this is a good way to provide high-quality LED without spending too much but you obviously need knowledge as you will have to build them and fix them if they break.

LED Maintenance

LEDs don’t need maintenance at all other than cleaning it after each cycle. A good quality LED will need a long time until it needs any kind of repair and usually, they consist of hundreds of individual LEDs, so it shouldn't be super expensive to change a small LED diode.


LEDs are more efficient than bulbs, being able to produce the same intensity with up to 70% less energy. You will need to provide good airflow and exhaust either way but the LED light won’t produce heat, although they can bleach your plants if they’re too close.


This is where LEDs take the cake. While each type of light bulb produces one light spectrum, one single LED fixture can produce all the wavelengths, providing a full spectrum of light for your plants.


Indoor lights for Cannabis grow: LED Lights in Grow Tent

Full spectrum LEDs in an indoor tent.

This means you won’t need to change anything other than the light cycle when transitioning to the flowering stage. If you’re using a good LED, you will see the difference in the growth, quality, and overall health of your plants.

The Difference Between Full and Mixed Spectrum Led Grow Lights

There are 2 main categories when it comes to LED grow lights, and both come with their own set of advantages and disadvantages. The 2 options are “full-spectrum” (also known as “broad spectrum” or “white LEDs”), or “mixed spectrum” (also known as “ narrowband spectrum “ or “blurples"). Let's take a bit of a deep dive into both options.

Full-Spectrum Led Grow Lights

Plants (including cannabis) love a wide range of light wavelengths. But, for photosynthesis they in particular like the band between 400 and 700 nanometers. This is commonly known as the PAR range (Photosynthetically Active Radiation). As the name may suggest, full-spectrum LED grow lights cover the entire range of natural sunlight. This includes the 400 to 700-nanometer range, plus all others. Full-spectrum LED lights try to mimic the sun as closely as possible, but this can cause some of that energy to be reflected off the plant itself and be wasted.

Let's quickly look at what the different light wavelengths do in helping plant growth.

Far Red Light (720 – 740 nm)

This range of light passes through the denser upper canopy and helps the growth of the lower parts of the plant. It can also help in speeding up overall flowering time and helps the plant produce the largest possible fan leaves.

Green Light (500 – 600 nm)

This range also helps in lower canopy light penetration. While it is within the photosynthetically active waveband of 400 to 700 nm, it is thought to have a less obvious effect than that of blue or red light.

Blue Light (400 -520 nm)

This range has a heavy effect on the photosynthesis of a plant, but overexposure can cause issues down the line. It has a direct response to the amount of chlorophyll present in the leaves and the leaf thickness.

Red Light (630 -660 nm)

This wavelength is thought to have the biggest impact on flowering and seed germination rates and is essential in boosting strong stem growth.

The old myth that only the 400 to 700 nm range is useful for cannabis cultivation is slowly but surely being overturned. With the wave of cannabis legalization slowly but surely sweeping the globe, more and more legal, peer-reviewed research is being conducted. These studies are showing that the full spectrum is important for complete cannabinoid and terpene production. Another pro of full-spectrum grow lights is the fact that it is much easier to identify issues such as nutrient deficiencies, pest problems, and disease.

Mixed Spectrum Led Grow Lights

This style of grow lights has a much narrower and more targeted band of the light spectrum offered. This means that less light energy is wasted, but also means that some of the important wavelengths may not be present. There are many cannabis cultivators that swear by “blurples” (named as such for the pinkish/purplish light they emit), but with the newer research being conducted it's pretty clear that the award for best-LED light goes to full-spectrum LEDs. That's not to say that narrowband spectrum grow lights won't work, on the contrary in fact. They do a fantastic job and can help you produce huge yields. They are much cheaper than full-spectrum LEDs, and can make a huge difference in the overall setup costs. So, which style of LED grow light should you choose? Well, that's a hard question for us to answer. You need to weigh up all the pros and cons and come to the right decision for yourself. But, if you can afford a full-spectrum light then they are pretty hard to pass up!

3. LEDs vs Bulbs

Independently on the type of light you choose, we recommend buying a good quality one. Remember, light is the main factor in plant growth, it will directly affect your plant and can be the decisive factor in a successful harvest. As a general guide, we recommend going for a bulb fixture if you’re growing 2-3 plants for your own consumption, as you will have a low initial cost. They’re also recommended if you’re dealing with low temperatures.


Indoor lights for Cannabis grow: LED Fixture

Good LED lights will keep your plants perfectly happy and healthy.

LEDs are recommended when you have a big budget to spend on your grow room and want to save a couple of bucks on the light bill. Or if you’re growing in a place where it’s illegal, you may want to keep the energy consumption down without losing quality. It is also recommended if you’re growing in a hot climate and want to avoid the use of an air conditioner. In this futuristic day and age of cannabis cultivation, many indoor gardeners are using a mix of HID and LED lights to offer the benefits of all the different lighting types. They all have their place and their use. So, why not take advantage of all the tech on offer, and grad a range of lighting options for your next indoor setup?

4. In Conclusion

The final decision will mainly depend on your budget and the space available. Bulbs can be better for a small number of plants while LEDs are better when you need to grow a lot of plants in a small space. That is because LEDs are smaller and you can fit up to 2 or 3 in a grow tent, while a light fixture is relatively bigger and can be hard to fit more than one in most tents. Another thing to have in mind is the cost. If you’re going for a bulb fixture, the initial cost will be lower but you will see quite an increase in your light bill. And although LEDs may have a high initial cost,  they consume so little energy that you won’t see a big difference at the end of the month.

25 April 2022