Lighting In Cannabis Cultivation: HPS Vs LED

Posted on Dec 26 , 2019

The HPS lights, high sodium pressure, have been the most used until today in the cultivation of indoor cannabis. However, with the cost of LED going down and technology of LED improving, growers are growing more with the new LED lights and therefore the LED horticultural lighting industry is expanding rapidly.

In this article we want to put both lighting systems on a scale and assess the advantages and disadvantages of each one of them, hoping that it will be helpful for those who grow indoors.

What are HPS lights?

Growing cannabis with HPS lights

High-Pressure Sodium Lights, HPS, emit light by sending a pulse of high voltage energy through a pressurized quartz tube filled with vaporized sodium, attached to other elements such as xenon or mercury. When these gases get hot they emit light. Sodium produces an intense light of a yellow-orange color, which can be mediated by xenon and mercury, since they emit light at the blue end of the visible spectrum, producing a whiter final spectrum.

HPS lighting systems have always been the best lights to illuminate the cultivation of cannabis. These systems usually have a power of between 75 and 4,000 watts and have perfect levels of CBT to grow cannabis, producing a significant amount of lumens. They can be found in different shapes and sizes, making it an option that can be perfectly adapted to the crop.

The efficiency of HPS lights

The highest performance HPS bulbs produce about 150 lm / W. For example, GE Lucalox 600 bulbs produce 90,000 initial lumens, these initial lumens refer to the average light output in the first 100 hours. In terms of PAR output of wavelength between 400-700nm, a best double-ended 1,000-W HPS lamp with an electronic ballast has a PPE of around 1.7 µmol/J.

HPS light spectrum

Although HPS lighting technology has been improved lately, its daylight imitation is considered to be worse than other newer systems. Since the sodium vapor emits an intense reddish-yellow light, although there are now new full spectrum light bulbs consisting of a double arc system comprising both a metal halide and an HPS component.

Advantages of HPS lights

  • Normally, HPS lamps produce an important stimulation of flowering, so that plants bloom more vigorously, which translates into better yields.

  • Initially, HPS lighting systems have less cost than LEDs.

  • HPS lights are more frequent and standardized, therefore they are easier to handle and you can know better what kind of lighting you are buying.

  • With HPS lights we are providing quality light to plants since it is a very powerful light.

Disadvantages of HPS lights

  • As we have said before they are cheaper than LEDs, but they consume a lot, so their operating cost is quite high, especially when the bulbs are more than 1000W.

  • HPS lighting produces a lot of heat, which does not require adequate ventilation. This heat is not highly recommended for small crops.

  • Frequently they need a ballast or reflector for their operation.

  • Its lifespan is shorter than those of LED lights.

What are the LED lights?


GLMX720 720W Full Spectrum LED Grow Light

The LED lights, light emitting diode, are semiconductors that allow electrical energy with little resistance in one direction and high resistance in the other, pass through a "pnjunction". On one side of the junction, there is a material treated to provide extra electrons, while on the other side there is a material that has been treated to have no electrons.

When voltage is applied, extra electrons move through the junction to fill the "electron holes" on the other side. This allows the light of a color that varies depending on the material used to be emitted. The most commonly used materials are phosphides and gallium nitrides, aluminum, zinc, and silicon.

The efficiency of LED lights

In LED lights the proportion of lumens per watt is less significant than the PAR. This is because the red and blue color has less proportion of lm/W generally because as it provides the most necessary bands for photosynthesis,  unnecessary waste of energy is avoided. The PPF for LED products ranges considerably, and many new fixtures now exceed 2.0 µmol/J.

LED lights spectrum

The newest LED lights use multiple bands to create a more complete, more complex and effective spectrum, which is thought to be very beneficial for plant growth and often use white individual LEDs along with some reds and violets. LEDs may provide the best spectrum for plants and the most modern full-spectrum models offer up to 11 bands of wavelengths of light, ideal waves for cultivation.

Advantages of LED lights

  • Today, quality LED lights can provide the same quality and intensity as HPS lights.

  • They produce very little heat, so ventilation may not even be necessary for the growing room.

  • These are energy-efficient lights and do not need as much electricity as HPS lights, so the electricity bills will be lower and the crop will not raise suspicion.

  • LED lights have a very long lifespan, between 50,000 and 100,000 hours.

  • A large number of growers claim that LED lights produce buds of higher quality in flowering, with a considerable increase in potency.

  • No ballast or reflector is necessary for its operation, since they are smaller systems, with the consequent saving of space.

Disadvantages of LED lights

  • At first, they can be very expensive compared to HPS.

  • There is no standardization in the field of LED crop lights.

  • As there is no regulation, we can find cheaper lights but they do not have the same quality, producing less than expected, which gives the LED lights a bad image.

  • Low heat production can become a disadvantage in cold areas, where lighting plays a very important role in maintaining a good temperature.

  • Although the quality of the outbreak is better, generally the LED lights give a lower production in terms of quantity.


As you can read, each lighting has its pros and cons. The debate about its quality is becoming less important, and everything will depend on the needs of your crop. Generally, depending on the initial costs, HPS lights are possibly the best for an amateur grower with few plants. But when money is no problem and you need long-term efficiency, perhaps the most suitable are LED lights.

Anyway, it must be said that the HPS lights are being dethroned, gradually leaving room for LED lights. Although similar results can be achieved with both, we must think that the HPS lights have already been developed to their maximum point and that the LEDs are in full development, so what will the future hold for us?

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