Whether you’re a seasoned indoor grower or you’re starting for the first time, you may have heard about the debate between LED grow lights vs. HPS grow lights.
This is a common question for indoor growers, specifically cannabis growers, and you want to make sure you have the right light for energy efficiency, high yields, and healthy plant and flower shape.
This article looks at the different factors of these grow lights, including light intensity, light penetration, yield potential, energy efficiency, overall price, and the upfront cost. By the end of this post, you will understand these different options and know which type of light makes the most sense for you.
And if you don’t want to go into depth on it, that’s fine too. We provided a simple explanation of which option we recommend in most situations below.
Before You Read Further
The debate between HPS and LED lights is still pretty heated, and there is legitimate evidence on both sides. In this article, we’re attempting to wade through some of the evidence provided by both sides and give you the tools to buy the best lights and get a better yield on your indoor garden. If and when more data or technology become available, we will update this article as needed.
Help us grow! This post contains affiliate links, which means we receive a commission if you click a link and purchase something recommended. All opinions however are our own and we do not accept payments for positive reviews.
LED Grow Light Vs. HPS
For most indoor growers, the modern LED grow light is usually superior to HPS lights or other HID options. The light emitted from an LED gives plants a better balance of red, blue, and green (similar to natural sunlight). It also produces higher plant yields using less power, lower electricity costs and requiring fewer additional costs.
While HPS bulbs are usually a cheaper upfront option, once you consider the cost of the fixture, additional costs of HVAC, and ventilation, LEDs are the best option and most affordable option in the long run.
There are a few exceptions to this, and there are still good lights within the HPS fixture camp. But an LED system usually is your best option in terms of performance and cost savings.
Here are some of the best small LED grow lights on the market regarding PAR output per watt, based on a study completed by MIGRO in 2021.
Of the options listed above, most are available on Amazon, so I included a comparison chart of those below:
The Best Small LED Grow Light
Unfortunately, MIGRO wasn’t one of the options on Amazon. So you can purchase from them on their site.
Let’s go into the definitions and factors that led us to this decision.Are these options too big for your needs? Looking for a small indoor grow light? Start with this post.
Why Is This So Complicated?
We’d be lying if we said the information below is simple. But to accurately compare these two systems, we have to take a step back and look at a few basics of grow lights. Notably, we need to first understand how efficiently a lighting fixture uses electricity and emits light. Then we need to know how effective that specific light is at reaching the canopy of your plants and then giving them the correct spectrum of lights. It gets even more complicated when you consider that different types of plants have different needs, and the spectrum of lights can affect the shape and flowering capabilities of those plants.
And finally, you have to think about the additional accessories that come along with your fixtures. HID units produce a lot of heat, so you can usually expect to pay more on additional equipment and electricity to keep your growing space cool and ventilated.
Dr. Bruce Bugbee, the founder of Apogee Instruments, was interviewed in 2018 on the MIGRO lights Youtube channel discussing the differences between HPS lamps and LEDs. If you have the time, please start by watching this full interview:
Grow Light Basics
When using grow lights, there are a few primary considerations regarding quality: the color of light, the energy cost of light fixtures, and light intensity. Before we look at the battle of LED grow lights vs. HPS, let’s start by understanding the needs of your plants.
Color Of The Light
We all know that plants use light to grow – but have you ever thought about how the color of light affects your plant growth?
The sun emits the entire spectrum of seeable light, which includes red, orange, yellow, green, blue, indigo, and violet. This is what we call full-spectrum light or white light.
When it comes to artificial light, most indoor plants thrive under full-spectrum bulbs, which generate a balance of cool and warm light that mimics (or at least tries to mimic) the sun. They’re great for seedlings, houseplants, culinary herbs, and a variety of other plants.
In broad terms, blue light specifically helps support leaf and stem development. Red light benefits flower growth, so it’s essential for plants that produce fruit. That said, there’s a lot of information out there about the specific benefits of red and blue lights. And some of it is misleading.
Here’s a good video on common misconceptions around the color spectrum, specifically red and blue light.
Lumens vs. Par
While it may seem obvious, it’s easy to forget that plants and people perceive light very differently. Humans perceive color using photopic vision. Plants use photosynthetic active radiation (PAR), which is the wavelengths of light that drive photosynthesis. Here’s a wonderful article on the differences between PAR and lumens.
Grow Light Intensity
The total quantity of grow light produced by an LED, HPS, or other light source per second is measured in PPF (Photosynthetic Photon Flux). This is what we would call the grow light intensity. Micromoles per second (umol/s) is the unit of measurement.
How Much PAR Does The Light Produce?
PAR (photosynthetic active radiation) refers to the wavelengths of lights that drive photosynthesis in plants. To measure the amount of PAR produced by a system per second, we use Photosynthetic Photon Flux (PPF).We should point out that PPF does not tell you how much of the measured light reaches the plants, but it is crucial to know if you want to figure out how efficient a lighting system produces PAR.
How Much PAR Reaches Your Plants?
To measure the amount of instantaneous PAR that goes from your fixture to your plants, something called photosynthetic photon flux density is used (PPFD). This a measurement of the PAR that arrives at the plant from the lighting fixture.
To add more to this complexity, you need to take several PPFD measurements on a growing area and find the average. The reason for this is that grow lights are typically the brightest in the center, with the light decreasing toward the edges of the area. It’s possible (and likely) that a grow light manufacturer only provides the PPFD from the center space. As an article from Fluence explains, “To ensure you are getting actual PPFD values over a defined growing area, the following needs to be published by the manufacturer: measurement distance from the light source (vertical and horizontal), number of measurements included in the average, and the min/max ratio).”
The strength or amount of light produced by a particular lighting source is referred to as light intensity. It is a measurement of a light source’s wavelength-weighted power.
The lamp source determines the light intensity, and there are high and low light intensity fixtures, lamps, and bulbs.
When it comes to indoor gardening, different light intensities have different purposes. Young plants, for example, typically need lower light intensity than vegetative and flowering plants.
Full-spectrum light source is intended for full-term plant growth from the vegetative stage to the higher-light-requiring bloom and finishing stages。#Fullspectrumled #Growled #Growlights #Ledgrowlights #Ledgrowlighting #growers #grodan #Agriculture #Backyardgarden #Cannabisgrow pic.twitter.com/I8RoJnTda7— Alisa Luo (@AlisaLuo4) July 1, 2021
Definitions: HPS Vs. LED Grow Lights
HPS lights, or high-pressure sodium lamps, are under the umbrella of high-intensity discharge (HID) lights. HPS systems have been the industry standard for a long time, as they were more affordable, have high intensity, and produce significant red light.
They also provide a large amount of yellow light and are commonly used for street lighting and security lighting. For many years, indoor growers and greenhouse growers favored HPS lights because of the massive outputs of the wide color spectrum produced by the relatively affordable lights.
During the flowering stage, red light is critical, and HPS has been shown to boost harvest output.
That said, the high-intensity output of High-Pressure Sodium lights generates a lot of heat. Because of this, you often need to have additional ventilation, fans, and HVAC systems to regulate temperature and keep the needed airflow. This can cause your expenses to rise quickly.
In many circles, one of the primary critiques of HPS lighting is that it doesn’t produce enough blue light, which can make a significant impact on the plants, causing them to stretch.
While HPS has remained the king of grow lights for decades, its reign is quickly coming to an end. HPS lights, as a whole, have not improved for many years. On the other hand, LEDs have drastically improved in the last couple of years, making them more effective and more affordable.
What Are LED Lights?
LED stands for light-emitting diode. LED grow lights are luminaires that create light for growing plants by efficiently utilizing energy. To work, LED fixtures use two semiconductor materials – one that’s charged positively (protons) and one that’s charged negatively (electrons). These two particles combine, and energy is released as a photon. The amount of energy released determines the color of the light. The light is then directed in a specific direction and emitted.
Here is a brief video on how LED lamps work:
History of LEDs
Henry Josef Round reported the first light-emitting diode (LED) more than a century ago. However, the development of LEDs did not begin until the 1960s, when red LEDs were first employed in commercial electronic products such as TV signal lights and remote controls.
LEDs have advanced rapidly since the 1990s, and they are now being considered viable alternatives for traditional lighting sources in greenhouses.
It wasn’t until recently that researchers could achieve greater emission power and make LEDs produce white light (full-spectrum light).
This new LED form uses less energy and produced much less heat than traditional incandescent lamps or HPS lamps. LEDs are also entirely made up of solid elements and can be made incredibly small.
What’s more, they can be customized, meaning you can emit any color of visible light on the spectrum in many cases. This smart lighting means you can manipulate the spectrum to better meet the needs of your plants.
Honorable Mention: Ceramic Metal Halide (CMH)
While we’re comparing HPS and LED lights in this article, we thought it was worth mentioning ceramic metal halide lights, which fall under the HID umbrella. They produce blue spectrum lights, which are great for vegetative growth. Overall, CMH has an excellent spectrum of light, very similar to LEDs.
What Are The Best LED Grow Lights?
Like everything, what’s best for one person may not work well for another. That said, here are some of the overall best LED grow lights on the market, broken out by use and price.
We’ve used data from MIGRO for this comparison. If there’s any question about the objectivity of MIGRO, seeing as they sell systems of their own, we should note that they list their own products as being in 4th place for best value by PAR output per $, and in 2nd place on the best value after three years.
The chart below considers the cost of the light vs. the PAR output (µmols/sec usable PPF) divided per dollar before taxes and shipping.
Here’s a comparison price of the products available on Amazon.
The chart below compares the initial cost of the LED fixture and the cost of running it with electricity, using 750µmols/m2/sec, for three years. What’s interesting about this chart is that some of the more expensive units – many of which had lower rankings in the chart above – make up some ground in this comparison. Top-quality and higher-efficiency fixtures often have lower running costs, bridging the gap with some of these initially more affordable options.
LED Grow Lights Vs. HPS: Breakdown
Like all things, it depends. But below, we’ve broken down the winners and losers for these two lighting systems. We should point out that this is the normal situation, but there could be specific products in either the HPS or LED camps that are outliers.
LEDs are the clear winner in the indoor growing space in terms of energy efficiency, especially compared to HPS lights. High-quality LED grow lights can provide comparable yields to HPS grow lights while using substantially less energy.
DelviroGrow completed a study in 2018, in which they compared ten 1000W HPS lights vs. ten 600W LED lights fixtures, specifically on cannabis plants. They found that LEDs was 40% savings when using LED grow lights vs HPS. LEDs are more energy-efficient, meaning they are more eco-friendly and affordable to run than HPS competitors.
Plight provided an interesting statistic on this, saying that “HPS will deliver approximately 34% of that energy in the visible light wavelength, while the LED will deliver 40-50% of its BTU energy as visible light.”
LED lights typically produce minimal radiant heat, near or around 11%, while HID lights can produce a significant amount of radiant heat – close to 55%. In other words, LEDs don’t generate as much heat as HPS light bulbs in most situations.
All this said, there are several situations where indoor gardeners could want their lights to produce heat. After all, the temperature is one of the most critical environmental factors for growth.
If you’re growing a plant that thrives at a greater leaf surface temperature, you should consider radiant heat when choosing your light source. In that situation, an HPS or other HID lighting fixture could be the best choice.
Winner: LED Lighting Fixtures
Best Light Penetration
The evidence in either direction is a little tricky. Overall, older versions of HPS outperform LED, but newer LED versions now match or overtake HPS lights.
LEDs are widely known to emit more light, but some research suggests that HIDs provide a more steady quality of light with better plant canopy penetration. This means that more light can travel below the canopy of your plants, allowing them to reach the lowest leaves and stems for better growth.
Growers must adjust the lights as their plants develop to maintain the proper overhead clearance for growth. LEDs do not always project well over long distances, so growers must change the lights as their plants grow. Fortunately, they produce less heat, so they can typically be closer to your plants.
The ideal distance varies depending on the lighting system and the plant. To put it another way, the light intensity near the diodes is significantly higher than it is a foot or two distant. In general, the variation in intensity for an HID bulb is substantially smaller. Plants get enough light from HIDs even when they’re further away from the light source.
Here’s a general rule of thumb for how far away your grow lights should be from your plants.
HIDs have proven to be trustworthy. In your grow tent or greenhouse, they can boost plant output, growth, and productivity. HIDs are also more widely used, in addition to providing consistent light quality.
Winner: Toss Up
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Easiest To Customize
One of the most extraordinary things about LEDs is that they are typically easy to customize the light for specific plant needs. These diodes can be targeted to a particular wavelength along the photosynthetic spectrum (visible and non-visible). This means you could customize your lights to have more blue diodes or red diodes.
Easiest To Use
I know we’re saying it a lot, but LEDs clutch this one too. You often need more equipment with HPS lighting. With an LED light, you don’t need to worry as much about HVAC systems, ventilation, lamp hoods, or separate bulbs.
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Lowest Upfront Cost
HPS lights typically have a lower upfront cost than LED lights. That said, LED technology has been closing the gap since the early 90s. In the battle of HPS vs. LED, high-pressure sodium lights take the cake…for now.
Lowest Overall Cost
The cost comes down to a few factors: efficiency and fixture cost. Similarly, the longer-lasting the bulb/fixture, the more affordable your costs will be over time.
Per watt for a traditional wattage fixture, HPS lighting is cheaper. But once you consider the cost of electricity – both for the fixture and the accessories, LED lights regularly save you the most money over time.
LEDs not only save money by being more energy-efficient, but they also last longer. Many LED grow lights come with a 50,000-hour warranty. A single LED grow light might survive over ten years or perhaps longer, depending on how long each light is turned on each day. MH bulbs last about 10,000 hours, while HPS lights last about 16,000 hours.
LEDs not only have a longer life expectancy, but they also keep their brilliance. Growers may need to replace HIDs even sooner as they become dimmer as they are used. The longer service life of LED panels may assist in offsetting the higher initial price.
While the comparison is complex, LEDs have become better and more affordable lights over time, while HPS fixtures have stayed about the same in terms of efficiency and quality. While HPS lamps are still primarily used in many commercial growing systems, they will likely be replaced in time by more affordable LED options in the years to come.