LED vs HPS: Which grow lights give the biggest yields?

Most cannabis growers know that the type of grow light matters. Not all grow lights give equal results when it comes to cannabis. Between LED vs HPS, which one do you think would work better for you? Which grow lights give the biggest yields? Let's find out!

Both LED and HPS have their pros and cons, and it is up to your needs which one you would choose. Some lights are perfect in one situation and other lights are perfect in a different situation. What grow lights you would buy, depends on several factors:
  • What does your grow room look like?
  • Are you growing clones and seedlings?
  • What is the temperature in your grow room?
  • How big of a budget are you working with?

When choosing a grow light, growers usually make decisions based on the wattage, and the price of the lighting system. However, another important factor is the PAR light value which shows us the amount of the light plants actually get to absorb.

In other words, the plant needs the light that is in the right spectrum so the plant can absorb the appropriate amount and type of light, and not all lighting systems are capable of doing so.

Truth be told, not everyone makes decisions based on the best case scenario. Some people like to stick to the true and tested stuff, while others are more open to trying out new stuff.

“ It’s got some limitations to it (LED), but it has improved. They use less electricity, they’re more efficient, and you can dial in a spectrum for them. I mean a light spectrum (the colour in the spectrum). They’re going to be around for a long time.”, (2017) - Jorge Cervantes

LED vs HPS: What yields more?

Back in the past, HPS lights were considered the best lights for indoor growing. Today, HPS lights are good for large-scale growers and commercial purposes since they cost less upfront. Thanks to the raw light output, they are very popular for high-ceiling grow rooms as the canopy needs to be quite far from the light to avoid light burns.

The LED vs HPS debate is an old one. But the general opinion is that it depends on what you are comfortable with. Many growers have been using HPS for years and have a good understanding on how to get the best out of them. They adjust their training techniques and much more accordingly. So if you are that person, keep up the awesome work!

It’s also worth mentioning that a lot of the opinions on LED grow lights is based on growers trying them a few years back when the technology was not there yet. Needless to say that in the last 5 years we’ve seen tremendous improvements which make LED grow lights the best option on paper.

Ultimately, if used correctly both systems can compete very closely however because the coverage of LED grow lights is often more even across the canopy many growers are seeing heavier yields with LED.

HPS grow lights

HPS stands for high pressure sodium. HPS grow lights have existed on the market for about 50 years, Their old fashioned technology is what makes growers keep using them or turn to new types of grow lights, such as LED lights. HPS lights are a proven solution, with loads of information surrounding their optimal usage. They provide stable results and switching from one brand of HPS light to another does not make a radical difference.

HPS grow lights are most often sold in 4 variants as:

  • 250W HPS grow lights
  • 400W HPS grow lights
  • 600W HPS grow lights
  • 1000W HPS grow lights

What’s good about HPS grow lights is that they have an abundance of light within the red and orange wavelengths. Thanks to this kind of wavelength, it makes it an optimal solution for flowering. These grow lights have raw light output, and they can really produce a great amount of light that is required for cannabis to flower properly.

HPS lights may perform somewhat better than LED lights if you live in a cold environment, because most plants don’t cope well with the cold weather and lights with high heat output such as HPS can prevent your plants from freezing.

The downsides of HPS

Compared to LED lights the cost of electricity is almost twice as much. So in the long run HPS can cost a lot, especially if power is expensive in your area. Bulb replacement and maintenance is something that will also add up long term. Each 10 months you should replace the bulbs for optimal performance.

Additional climate control. Unless you have a greenhouse in the winter and plan on heating the space with your lights, HPS produces generally too much heat for most environments. This means additional devices such as AC systems will be required to keep the desired temperature. This not only adds up the cost of the device itself but also the power usage of it.

To power the bulb you will need a ballast and a reflector which adds to the bulkines and complexity of this option. Some growers even use dedicated ventilation systems to cool the reflectors so you can see how quickly this becomes more complex and pricey than expected.

HPS is often only used with flowering plants. In other stages, growers often use Metal Halide lamps - so you might end up with two sets of bulbs to cover a full cycle. This is the best way to provide your plants with the suitable light spectrum.

In comparison, LED grow lights often feature a “Full-spectrum” technology which gives all of the colors at once (like sunlight basically) so you can use the same fixture from seedling to harvest. Some HPS use hazardous components such as mercury in their builds so be careful.

 

Why is HPS better for flowering?

HPS is optimal for flowering when compared with other bulbs such as MH and CMH. Since these grow lights have red and orange wavelengths, they make the flowering process faster and the yields bigger.

The type of light HPS lights produce is mostly red and yellow, as you can see from the image below. This type of light promotes flowering and increases bud size and density.

One of the most common mistakes growers make when choosing a grow light is going for the system which has the highest Watt number, and the lowest price thinking this would effectively increase their yields.

Not every grow setup using HPS lamps needs a 1000W lamp. If you can, invest in a PAR meter such as the Apogee MQ-500 to measure the PAR values on your canopy. You should aim for values between 700 and 1000 to avoid light burn.

LED grow lights

LED grow lights can last longer than HPS lights and they use less electricity so they are definitely more affordable in the long run. They are perfect for seedling and vegetative stages of growing, but also perform amazingly in the flowering stage.

Unlike HPS lights, LED grow lights don’t emit so much heat, which is particularly important in growing areas with warmer climates. You will still need to buy a ventilation system, but it will be significantly easier to manage the heat.


Probably the biggest reason why LED lights are so popular is the fact you can provide the full spectrum of the light to your plants. Every diode in a LED light can have a light of different color spectrum, for instance red, purple and white - all at the same time or in some instances they can be tuned to your needs.

On the other hand, not all types of LED lights have the same qualities and they are not standardized like HPS lights. When buying a LED grow light consider the brand, PAR value and the light spectrum as the main factors.

LED lights are usually more expensive than HPS lights, but down the road you would have less operational costs including electricity bill, maintenance or buying new lights every other year.

Why do so many growers use LED grow lights?

LED grow lights are very popular among cannabis growers for the following reasons:

  • Low heat emission
  • Easy to use and modern-looking
  • Full spectrum of light
  • Even coverage of light

LED lights are budget friendly because you don’t need to buy new bulbs every time you need a different light, as they have a full spectrum of colors from blue to red. Not to mention that the electricity bills are lower compared to the grow rooms that use other lights. First time growers mostly turn to LED lights as they are very easy to use and no prior growing knowledge is needed.

Which type of grow light has better coverage?

As previously mentioned, regardless of the wattage, the one thing you should focus on is PAR. This will tell you exactly the amount of usable light for your plant.

By hanging the light at different heights you will get different results, for instance an HPS can’t be placed very close to the canopy or else it will concentrate too much light in the center and burn the plants there.

Compared to that an LED can be placed closer to the plant and some designs like Bar systems are specifically made to distribute light evenly. In the end you don’t want any value below 500µmol/(m2s) and anything above 1000µmol/(m2s) will be too much unless you supplement CO2. In this case you can go as high as 1500µmol/(m2s).

Here is a rough example of how different the light coverage can be between both fixtures.

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