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?
Author Enzo Schillaci
05 June 2020
8 min read
Indoor lights for Cannabis grow: LED vs Bulbs

Contents:

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. Light Bulbs

Light bulbs are the “classic” grow light. They were the first type of light used for the 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.

 

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.

Cost

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:

Ballast

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.
 

Note: 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.

 

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.

Air Cooling

When growing a lot of plants, you will need more wattage. 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.

 

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.

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). 

 

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.

Tip: 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.

Temperature

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.

Tip: If you’re growing in a cold place, light bulbs can help you keep the temperature up.

Spectrum

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

 

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.

Note: 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. 

 

 

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.

Cost

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 with their plants.

Note: 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.

Temperature

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.

Spectrum

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 light for your plants.

 

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.

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.

 

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, as 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.

4. In Conclusion

The final decision will mainly depend on your budget and 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.

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