grow lights explained

Best lights for growing weed – introduction to indoor grow lights


It’s been a long time since the first indoor grow attempts, and things have changed a great deal since then. Every parts of our setups have considerably evolved, taking advantage of the latest technologies and scientific research.

When reviewing the different types of lights which were used and are still used today, one can only appreciate that evolution. Between basic incandescent bulbs and LED there is a whole range of products, and I will try to help you understand what they are all about. But first, we have to go back to the basics and look at how the light impacts your grow.


P.A.R (Photosynthetically Active Radiation)

  • It’s the spectral range of solar radiations used by the plants to achieve photosynthesis and recreated by the lamps. You can hear people referring to P.A.R per Watt in order to express a lamp’s ability to produce such radiations.


Watts and Lumens

  • They are the typical ratings most growers are familiar with, and they can usually be found on any bulb packaging. Watts represent the quantity of energy used to produce light, whereas lumens are used to measure the light intensity. The greater these ratings are, the more power you will use and the more intense will be the light.


Let’s now see what are the different types of lights available!


Incandescent grow lights

They are the basic light bulbs you can find in most houses, they are very inexpensive but also a poor source of light for plants and energetically inefficient. You should avoid them.

Fluorescent grow light bulbs

Fluorescent grow light for weed

Fluorescent grow light bulbs have been used for a long time now. They were considered as unhandy and having a low output because of their size and low intensity, even if some people managed to get great results, as they can have better color rendering properties (high P.A.R) than HID lamps. The S.C.R.O.G technique, for example, was implemented under this type of light and is very efficient.

But due to recent technical improvements you can now buy smaller and more intense fluorescent grow lights. Among them you can find:

  • t5 fluorescent grow lights

t5 grow marijuana lights

« t5 » refers to the size of the tube (5/8’’ in diameter). They are the most efficient tubes on the market. They have a low initial and running costs, a lifespan of 20,000 hours, a low heat output and  are able to produce up to 100 lumens per watt, which is nearly about the same than an HPS lamp.

  • CFL lights

cfl bulb

They use little power, produce little heat, have a life of about 10,000 hours, and produce up to 80 lumens per consumed watt. They are mostly used in small spaces or for propagation purposes.


Plasma lights

plasma growing light

These are lamps based on the system demonstrated by the famous Nikola Tesla, they don’t use an electrode to produce the light but act on sulfur plasma with microwaves. Since it’s the element that often breaks the first on regular lamps, they are considered to have a very long lifespan.

Despite this, they are not widely used by growers because of their low efficiency: they come at a terrible price and lack a whole important part of the spectrum useful to plants.

  • Magnetic Induction Grow Lights

Not really regular plasma lights and working rather like fluorescents tubes. They have an unmatched lifespan of allegedly 100,000 hours, produce high lumens and P.A.R per watt at a constant rate (they do not decrease with time), and have a small environmental impact.

The main problem with these is they have a poor light penetration and a very high price. Click here for full review of 6 best Plasma Grow Light.


H.I.D grow lights (High Intensity Discharge)

Well, here we are. These ones have been used for many years all around you in public spaces, stadiums, roads and so on. They are considered as the standard within the industry and among growers, for they are one of the best ways to convert power into light. They are the most widespread in grow rooms, have the deepest light penetration, and until quite recently, when new lighting sources were put on the market, they were seen as the most efficient lights to grow weed.

They come in many sizes, models, and are the most powerful ones you will find, up to 1000 watts.

How does it work?

High-intensity discharge lamps (HID lamps) use electrical gas-discharge to produce light. They create an electric arc between tungsten electrodes located in an arc tube filled with both gas and metal salts. The best known are:

  • Metal-halide (MH) lamps
  • Sodium-vapor lamps

Metal Halide

metal halide bulbs

Metal halide bulbs produce a light high in the blue spectrum, encouraging a compact, leafy growth. The average useful lifespan is about 10,000 hours. They produce up to 125 lumens per watt, and to be able to use them you need to a ballast, often integrated to the bulb.

High Pressure Sodium lamps (HPS)

hps bulbs to grow weed

They are the most commonly used among HID lamps. They also needs a ballast, which can be magnetic or digital and have a red-orange light used primarily in the flowering phase of your plant’s life. Their effective lifespan is  around 12,000 hours and the area covered is the same as for MH lamps, a 600 watt HPS bulb covering a space about 4’ x 4’, and 1000W HPS grow lights covering about 5’ x 5’. Due to increased demand, you can find bulbs matching different variation of the spectrum.

Common problems to both these lamps are their nasty environmental impact, and the great heat they produce, often requiring a specific extractor known as a cool tube, to maintain a bearable temperature for the plants.

The bulbs are frequently changed although they will continue to light up, but the emitted light will progressively lose intensity. Professional growers sometimes sell used one in bulks to people reselling them, so be careful when buying cheap hps grow lights!


Led grow lights

Marijuana led grow lights represent the biggest evolution we’ve seen during the past decade. They started quietly and now their market blooms as the manufacturers produce more efficient models every day.

The best led grow lights for cannabis allegedly consume less than half the power used by HID lamps for the same area and produce a spectrum matching exactly the plant’s need, all along its life, without energy loss. Highest-end models even include brand-new features, being able  for example to recreate the sunlight’s intensity, changing along the day.

They are a lot of led grow lights for sale, and in order to make the right choice I highly recommend reviewing a few models as the products are of very unequal quality and price, ranging from a few hundreds to more than 1500 $ for the most expensive ones.


Their main key features are:

  • High initial prices
  • Long lifespan
  • Low running costs
  • Very good spectrum and among the highest P.A.R per watt
  • Low heat production
  • Lower light penetration than HPS/MH



How to make the right choice?

Light for your growing space is the most important aspect of your setup, so you don’t want to rush and make a bad decision, as it will impact the quality and volume of your buds. Many aspects should be considered before making your choice:

  • Size of your grow tent or grow room you won’t go for the same depending on the space available.
  • Some lights are very expensive, but great results can be achieved with cheap lights, like fluorescent tubes for example.
  • Technique you plan on using.O.G and S.C.R.O.G are particularly efficient with low penetrating lights like LED or fluorescent.
  • Do you have enough air ventilation? HID produces a lot of heat, temperature can rise very fast and you need to be able to take it out.
  • What do you want to grow? You can use various light sources depending on the type of plants you grow, mother plants and cuttings can be grown under less intense lights, bigger bushy plants will rather need a penetrating light.


Here is a small chart so you might compare the pros and cons of the different systems we overviewed:


T5 fluorescent HID INDUCTION LED

-Low price

-Low heat

-Great spectrum

-Low initial cost

-Proven results

-High penetration

-Great spectrum

-No bulb replacement

-Great spectrum

-Long lifespan

-Lower energy costs


-Low penetration

-Bulb lifespan

-Heat output

-Bulb replacement cost

-High energy costs

-Initial cost


-Initial cost

-More recent, results need to be time tested



Much can be said about lights, and you will certainly meet people convinced that the type they use is the best.

Well, the truth is that there isn’t one great type; all of them have proven their ability to provide a decent yield (except perhaps the incandescent ones!) and the quantity of produced buds per watt

depends greatly on how it is used, and in which conditions.

So define your project and according to what we’ve seen, you should be able to make the right choice!

If you need to compare some models, on this site you can access the best reviews for your growing equipment.

Next Step: Purchase Marijuana seeds & Grow Tent

Now you have purchased your first grow light and the only thing missing is growing tent (you have several different options and you can  read more here to see what is best for your needs) and marijuana seeds that you can purchase from one of the marijuana seed banks and read reviews here.

If you are completely new to indoor growing read our guide how to grow marijuana indoors!

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