Grow Light Systems – the best tips for you

No matter how great or expensive your grow tent is, if you don’t light it properly, your plants won’t produce their maximum yield.

Much worse.

If the lighting is wrong, your plants can die or the tent burns down. Therefore, we will show you which grow tent lighting system & formats you need.

In this post you can find

Pre-calculated dimensions for your grow tent

Grow tent lightning systems : Calculating the dimensions

A successful grow needs the right amount of light. You can see with a match in a dark room, but a flower is unlikely to flourish in candlelight, we certainly agree.

The light intensity is given in lumens or lux. Lux describes the illuminance on a certain area. For this purpose, the light intensity is measured in lumens on a square meter area. This results in the formula 1 lux = 1 lm / m².

During the growth phase, hemp needs at least 15,000 lux. 25,000 lux or more is optimal. The plants need even more power during flowering. At least twice that, i.e. 30,000 lux. Ideally, your lighting creates 50,000 lux or more.

Calculate grow tent lighting
Calculation formula
  • Calculate the area of your tent: length x width
  • Check the number of lumens on your lighting ( watt) Lumen calculator )
  • Number of lumens / area = LUX
  • LUX should be more than 30,000.

Here is an example:

Your grow box is 60 cm x 60 cm = 0.36 m² in the base area. You are planning to buy a 250W HPS with 33,000 lumens for lighting. We now calculate 33,000 lm / 0.36 m² = 91,667 lux. That is more than three times the minimum output. With a side width of 80 cm, we still achieve over 50,000 lux. You can see that it only becomes tight from around 1 m² and you need a stronger lamp.

Grow tent : choosing the light source

Basically, you have a few options to illuminate Grow tent Light sources are a dime a dozen today and thanks to modern science we can also make use of economical and supposedly weak lamps.

In the following, we will briefly address the various grow tent light systems that can be used to illuminate grow tent. You can find a more detailed description on the individual pages for the respective light sources.

LEDs – the all-rounder

growbox beleuchten led

While HPS were long considered the means of choice to light your grow tent, now LEDs a popular alternative to growing * . These can best reproduce the color spectrum of the sun. In order to achieve an adequate light intensity, an LED also needs enough current.


  • Adjustable for grow and flowering phase
  • High luminosity
  • Suitable for every budget
  • Low power consumption
  • Very long service life


  • LED protective goggles recommended for operation
  • Big differences in quality (don’t go for the cheapest)

Grow Light Systems – the best tips for you 1

Our price-performance LED lamp winner – Sanlight*

The Sanlight LED Bars (2nd generation) offer an optimal light spectrum and precise light control.

A great advantage is the passive cooling, which means that the lights can be operated silently.

There is also a 3-year manufacturer’s guarantee.

Save an average of 5% compared to buying the individual parts – with the complete set.

It includes: 2x SANlight Gen2 LED bars, power cable
2x extension cables, 1x multiple plug for Q series
2x GrowPRO cable ratchets & 1x Legrand Omnirex timer

Probably the biggest advantage, the lower power consumption, only counts in part. Because even if high-quality LEDs now provide the same performance as HPS, they are significantly more expensive to purchase. A few hours of cultivation have to come about before the LED is worth buying.

There are also big differences in quality between different providers. LEDs are a good alternative for this, especially in the long term, as they have a much longer lifespan than HPS. So if you’re planning for the long term, you might want to consider LEDs.

Sodium vapor (DNL) or metal halide lamps (MHL) – the classic

Grow Light Systems – the best tips for you 2

Probably the most common way of illuminating a grow tent is the sodium vapor lamp. Even if you are not aware of it, you have probably seen one before. Tthey are often used in street lamps.


  • Perfect light spectrum to grow
  • High luminosity
  • Easy to build & operate
  • Inexpensive to buy


  • High power consumption
  • High heat development
  • Accessories necessary
  • Distance to the plants necessary (min 180cm)
Grow Light Systems – the best tips for you 3

Premium lighting set, Adjust-a-Wing – flowering / growth *

Sets from 250W include:

  • Reflector incl. Great spreader
  • electronic ballast
  • Osram NAV-T (bloom) & Venture Sunmaster (growth)
  • Easy rolls
  • analog time switch

150 W (standard set) * | 250 W * | 400 W * | 600 W * | 1000 W *

The advantage of a NDL, or a similar MHL in principle, is that it emits a monochromatic light.

As a result, by choosing the right lamp, we can serve exactly the light spectrum that we need to grow cannabis. In addition, HPS and MHLs have a higher luminous intensity than neon tubes, energy-saving lamps and LEDs. This is how the plants grow under ideal conditions.

The disadvantage of such light sources is that they generate a comparatively high amount of heat.

Since a large part of the energy is converted into heat and is thus lost, sodium vapor lamps usually have a higher power consumption. In addition, accessories such as a ballast, a reflector and possibly a relay are required in operation.

Neon tubes and energy-saving lamps – the cheapest method

growbox beleuchten leuchtstoffröhre

A cheaper way for lightning your grow tent are neon or fluorescent tubes or energy-saving lamps (ESL). These are particularly useful in the growth phase, but should not be used as the only light source in the flowering phase.

This is because they are not as bright as a HPS, MHLs or LEDs. On the other hand, they are much more economical in terms of energy consumption. In addition, ESLs have an integrated ballast, so that they can normally be connected directly to the electricity.


  • Good for the growth phase
  • No heat development
  • Inexpensive to buy & operate
  • High availability


  • Not suitable for the flowering phase
  • Low depth effect
  • Low luminosity

A cheaper way for lightning your grow tent are neon or fluorescent tubes or energy-saving lamps (ESL). These are particularly useful in the growth phase, but should not be used as the only light source in the flowering phase.

This is because they are not as bright as a HPS, MHLs or LEDs. On the other hand, they are much more economical in terms of energy consumption. In addition, ESLs have an integrated ballast, so that they can normally be connected directly to the electricity.

Fluorescent tubes dimension calculation

Fluorescent tubes also need a starter. Sockets including starters and the tubes can be obtained very cheaply and can be found in every hardware store. They are cheap and can be used as additional lighting later in the flowering phase to further maximize the yield.

It is important that the right light spectrum is used. Otherwise you can will need to illuminate your grow tent with 100 tubes and still don’t get the best result out of your grow. In our experience, fluorescent tubes are best for small closets, for growing or in closets with mother plants. You can learn more about this type of lighting here.

Energy saving lamp

Extremely compact design with high efficiency. Extremely fast luminous flux start-up thanks to Quick Light technology. Low maintenance. Higher light output. Pays for itself quickly. Up to 80% less energy consumption compared to conventional light bulbs.

Grow tent light systems : What do you have to pay attention to?

Now we come to the really important part of this page. Because no matter which light source you ultimately decide on, you should orient your choice on the following points in order to find the right light source for you.

Grow Light Systems – the best tips for you 4

Color spectrum (the blue pill or the red pill?)

The color spectrum is one of the main criteria when choosing a light source to illuminate your grow tent. The color spectrum is differentiated, as the name suggests, based on the color.

Above all, cannabis needs two spectra in visible light: blue and red. While blue light causes the plants to grow bushier and more compact and to form thicker stems, red light ensures that they grow taller but develop thicker buds in the flower.

Expressed in numbers, the following results. During the growth or vegetation phase you need more blue light with a color temperature of approx. 6000 – 8000 Kelvin. In the grow tent you want to keep the plants as low as possible. For this they should get as many leaves and shoots as possible.

In the flowering phase you change the light spectrum to more red light with around 2700 – 3500 Kelvin. In this phase, the plants usually do not gain much height and by switching to red light, particularly large buds form and the yield is maximized.

Duration of lighting – how much light does cannabis need?

In nature, cannabis doesn’t grow year round. The seeds germinate in spring and bloom towards the end of summer, when the days get shorter again. It doesn’t depend on a specific climate, but on how long the sun shines during the day.

We use this knowledge for indoor breeding. If we let the seeds germinate and grow the plant in the growth phase, we will illuminate it 18 hours a day. This is how we simulate the long days in summer.

Plants grow best with 18 hours of light per day. They get as much light as possible without harming them. Tests with longer exposure times have shown that there are no advantages. Less light is also not an advantage, since the full potential cannot be developed.

After the plants are ready to flower, switch to lighting for 12 hours a day. This simulates the end of summer when the days get shorter again. It is important that the sleep of the plants is not disturbed.

Calculate grow box ventilation

Even small light sources such as a red LED on the thermometer can affect the growth of the plants. Therefore, a good grow tent should be completely dark inside and not let in any light from the outside.

Distance to the plant

Also not to be overlooked is the distance between your light source and the plant. On the one hand, you lose a little light intensity the greater the distance to the light source, and on the other hand, a lamp that is too warm can burn the plants if the distance is too short.

Grow tent is especially true for HPS, which get very hot. This problem rarely occurs with neon tubes and energy saving lamps. They can be placed a few centimeters above the plants. HPS, on the other hand, should have a distance of at least 20 cm. But here it also depends on the wattage. The larger the higher the distance.

It is best to hold your hand over the top leaves and hang the lamp so high that it does not become uncomfortable on your skin even after prolonged exposure. If, on the other hand, it becomes too warm on your hand, the lamp is hanging too low.

The distance has to be adjusted again and again during the entire grow, because your plants logically grow upwards and thus reduce the distance to the lamp. The best way to hang your lamps is with chains or easy rolls. So you can easily adjust the height later.

Immediately after germination and in the first few days, however, too strong light can also be harmful. If you are using an HPS from the beginning, the interval should be more generous in the first 5-10 days.

What GrowboxTest recommends for beginners

We have made the best experience with sodium vapor lamps ( To the MHL / NDL test | Buy at * ). Both in the growth phase and in the flowering phase. A 400W lamp is completely sufficient for a 100x100x200 cm Grow tent and we could never complain about the yield. A 250W lamp is sufficient for smaller boxes. A 600W lamp is only worthwhile from a side length of 120 cm.

During the first days after germination and for the rooting of cuttings, we used fluorescent tubes. These have practically no heat development and the risk of burning your protégés is almost zero. You just have to pay attention to the correct color temperature. This saves a little electricity during the first few days, when high light intensity is not yet so important.

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