LED vs HPS.
It’s one of the most debated topics among indoor farmers because there’s no easy answer:
- LED lights boast tons of innovation and enviably low maintenance costs.
- HPS lights are powerful, tried, and true. And did I say powerful?
The truth is that there’s no single right answer.
Ultimately, it depends on your unique needs and setup.
And that’s why we put together this comparison.
This guide has everything you need to know about LED vs HPS lights:
- Complete 11-category comparison.
- How LED and HPS lights work.
- Pros and cons of both types.
- The exact kinds of people would benefit from each.
Let’s get started.
LED vs HPS Grow Lights: Quick 11 Category Comparison
We evaluated LED vs HPS lights across 11 different categories:
- Initial Cost
- Industry Standardization
- Light Spectrum
- Heat Production
- Light Penetration
- Seedling Phase
- Vegetative Phase
- Flowering Phase
Spoiler Alert: LEDs won by a 7-4 margin.
But the truth is that many growers swear by HPS lights, and for good reason. Depending on your setup, they may be the perfect grow light for you.
|1. Initial Cost
|LED lights often cost 3-5x more than HPS lights for the same output.
|LED lights are plug-and-play with your standard AC outlets whereas HPS lights require a ballast setup and proper air circulation.
|LED lights are new on the grow light scene and lack the industry-wide standardization seen with HPS lights, which have been used for decades.
|LED lights use about 40% less wattage to produce the same output, and their directional output requires no reflectors.
|LED lights last 50,000-100,000 hours whereas HPS lights last 2,500-5,000 hours before needing to be replaced.
|6. Light Spectrum
|LED lights are full-spectrum whereas HPS lights produce more long-wavelength red/orange light with little short-wavelength blue light.
|7. Heat Production
|LED lights radiate very little heat with built-in heat sinks, radiating at 107°F. HPS lights burn up to 5300°F and heat up a grow room by 15°F-25°F.
|8. Light Penetration
|LED lights are unable to penetrate thick foliage. HPS lights can penetrate deep.
|9. Seedling Phase
|LED lights are better for the seedling phase with softer, cooler light on the blue end of the spectrum. HPS lights are hotter and emit more light at the red/orange end of the spectrum.
|10. Vegetative Phase
|LED lights are best used with the Sea of Green growing method with plenty of short plants at even heights. HPS lights are best used with taller, bushier plants where their power can penetrate deeper, though they still aren’t optimized for the blue end of the spectrum.
|11. Flowering Phase
|LED lights offer an adjustable light spectrum and can be optimized for red and infrared provided crops aren’t too dense. HPS lights emit a ton of red light and are highly optimized for the flowering phase. When push comes to shove, production numbers tend to be better with HPS lights during the flowering phase.
LED Grow Lights: Pros & Cons
LED grow lights are the easiest and most energy-efficient option available, but there are a couple of important caveats:
- Quality full-spectrum LED lights can be expensive.
- There’s a lot of imposter LED grow light garbage out there.
For the purposes of this article, we’ll talk about the good stuff: true full-spectrum chip-on-board (COB) white LED lights.
(But there’s actually something better than just pure, 100% white LED lights. You can buy grow lights with red and blue diodes embedded in the panel with both UV and infrared wavelengths included.)
How do LED grow lights work?
There’s a lot of technical science stuff that goes into how LED lights work, but here’s the high-level summary.
LEDs create light by passing electrons along a one-way circuit through a semiconductor material with electron holes in it. As the electrons pass through the semiconductor material, they fill these electron holes and emit their energy as photons, the basic unit of light.
Depending on the composition of the semiconductor material, these emitted photos have various wavelengths.
|Aluminum Gallium Nitride
|Indium Gallium Nitride
|Indium Gallium Nitride
|Aluminum Indium Gallium Phosphide
|Aluminum Gallium Arsenide
|Red and IR
Take a quick look at the following image showing wavelengths and colors on the light spectrum.
(As a bonus, it shows optimal absorption wavelengths for both chlorophyll A and chlorophyll B, which are essential for the synthesis of glucose for plants’ metabolic processes.)
As you may have noticed, none of those five rows in the table above says “white.” That’s because white light is a combination of all wavelengths, so LED manufacturers need to do one of two things to produce white LED diodes from the single colors produced by each semiconductor.
- Combine red, green, and blue (the three primary colors) to produce white.
- Use a phosphor material to convert blue or UV light to broad spectrum white light.
This Wikipedia article does a great job of explaining those methods.
As complex as LED technology sounds, the core components of today’s LEDs trace their origins back over 50 years. If this quick description has left you wanting, check out these two awesome resources that explain things in all their nerdy glory.
Advantages of LED Lights
- Use nearly half the wattage to produce the same power as HPS lights.
- Last 50,000-100,000 hours before needing to be changed compared to 2,500-5,000 hours for HPS lights.
- Radiate virtually zero heat, which reduces both ambient temperatures and the risk of burning your crops.
- Come as plug-and-play boards that simply need to be plugged into your standard 120V outlet.
- Available in a wide array of spectrums for any plant in any growth phase (or all growth phases).
- Are both waterproof and dustproof.
Disadvantages of LED Lights
- Cost 3-5x more upfront to experience the long-term cost-saving benefits.
- Because they’re a relatively new option for growing, there’s little standardization across the industry.
- Many manufacturers advertise full-spectrum light when that isn’t the case.
- While low heat production generally is good, you may need to supplement your setup with heat-producing lights if you’re growing in colder conditions.
HPS Grow Lights: Pros & Cons
Even if you’ve never heard of or used HPS lights before, you’re definitely familiar with them. They’re the standard bulb used for streetlights!
HPS stands for “high-pressure sodium” and actually is a subset of a larger class of lights: high-intensity discharge (HID).
Let’s talk about HID lights in general before we talk about HPS specifically.
What are HID lights?
HID lights arc electricity across two tungsten electrodes, heating the gas inside and in turn emitting light. This is different than standard incandescent lights, which heat up a tungsten filament without arcing electricity across the enclosed gas.
There are three types of HID lights:
- High-pressure sodium (HPS)
- Metal halide (MH)
- Dual arc hybrid (HPS+MH)
While each varies slightly in terms of both design and function, they all operate using the same electrical arc across two tungsten electrodes.
What are HPS lights?
HPS lights produce a warm red/orange light with longer wavelengths mostly from 560-620 nm, which is the yellow-to-red part of the light spectrum. This part of the spectrum mostly is used by plants for floral growth, making HPS lights optimal for the mature flowering phase of plants like tomatoes and cannabis.
HPS vs MH lights
Though they both fall under the HID light umbrella, HPS and MH lights are very different. A quick look at the relative spectral power of both HPS and MH lights easily shows their differences.
But while MH lights emit more light in the blue end of the spectrum, some people disagree that there’s any tangible benefit for your plants’ vegetative growth.
Relative spectral power aside, there are several other notable differences:
- HPS lights produce 50% more lumens per watt than MH lights.
- HPS lights maintain lumens far better than MH lights and last twice as long.
- HPS lights contain 61% less mercury than MH lights.
Pound-for-pound, HPS lights are better than MH lights.
What about dual arc hybrid (HPS+MH) lights?
But there’s a third type of HID light that captures the benefits of both: dual arc hybrid lights with both HPS and MH components.
Usually, they come in the form of a 1000W light made up of a 600W MH tube and a 400W HPS tube.
The advantages and disadvantages of these dual arc lights are pretty obvious.
- Advantages: Conveniently get the best of both HPS and MH lights, most notably complete coverage of the light spectrum, in a single bulb.
- Disadvantages: Having weaker versions of both HPS and MH lights prevents either from working its full magic during their respective growth phases.
For the purpose of this article, let’s stick with HPS lights, which have a lot of advantages over MH lights, as we continue our LED vs HPS comparison.
Advantages of HPS Lights
- Have been used as grow lights for decades, allowing for plenty of experimentation and standardization among manufacturers.
- Cost 60-80% less at startup than comparable LED grow light systems.
- Produce a lot of strong, powerful light that’s ideal for penetrating thick foliage.
- Though heat often is a negative, there are applications where it’s beneficial, such as in cooler growing environments with substantial headspace.
Disadvantages of HPS Lights
- Much less cost-efficient to operate than LED bulbs, requiring nearly twice as much wattage for the same output.
- Last only 2,500-5,000 hours before needing to be replaced, which is far less than the 50,000-100,000 hours for LED lights.
- Contain mercury.
LED vs HPS Grow Lights: 11 Category Deep Dive
We gave LED lights the 7-4 edge, but there are still several reason to love what HPS lights offer. Let’s dive into each category.
1. Initial Cost
Let’s look at the startup costs for a 20 square foot grow space for LED vs HPS:
- LED: $899 (600W light)
- HPS: $308 ($189 for a 1000W light with ballast + $119 for a fan to circulate the air and cool the room)
And as you expand to bigger grow spaces, the gap between LED and HPS widens.
However, LED light technology is advancing rapidly and costs for high-quality, full-spectrum white LED lights continue to drop.
This is an easy nod for LED. These systems are plug-and-play with hanging the lights via the usually-included daisy chain being the hardest part. It isn’t that HPS lights are that hard to install, but there are more moving parts, including your airflow system.
3. Industry Standardization
LED lights have burst onto the scene over the last 5-10 years with manufacturers putting out new products and new LED configurations, including different blends of white, infrared, and UV light.
Because HPS lights have been the industry standard for decades, they’re well-understood and highly standardized.
A 600W LED light will give you the same light output as a 1000W HPS light, saving you 40% of the ongoing electrical costs.
But let’s look at efficiency in terms of cost as well.
First, you’re saving that 40% on electricity. That’s easy math.
Second, LED light setups don’t need some of the other maintenance equipment that HPS setups need, like fans to circulate air and regulate room temperature. (Remember, HPS lights generate a lot of heat.)
This awesome guide looked at the ongoing costs of operation for a massive 10,000 square foot cannabis facility and found that LED lights saved growers $1.16 million over five years for an averaging savings of $320,000 per year for that 10,000 square foot facility.
Undoubtedly, there are some economies of scale, but that analysis showed an annual savings of $32 per square foot. If you have a 20 square foot grow space, LED lights will save you around $640 per year.
This one is no contest. LED lights are rated to last 50,000-100,000 hours with negligible decline in performance over that span.
HPS lights generally are rated to last around 25,000 hours, but they decline in performance rapidly and should be replaced every 2,500-5,000 hours. (And MH lights are twice as bad.) Check out this grainy chart from this forum thread to see what I mean.
6. Light Spectrum
You saw this chart above, but it bears republishing here.
LED lights can be customized to produce light at all wavelengths from UV through infrared, targeting all phases of your crop’s growth with a single setup.
7. Heat Production
LED lights emit heat at just 107°F with very little impact on your grow room’s temperatures. HPS lights can easily push temperatures up 15°F-25°F depending on the wattage of your light, making proper air circulation essential. HPS lights also need more vertical headspace over your crops to prevent burning them, especially during more delicate seedling and vegetative phases.
8. Light Penetration
HPS lights seemingly beat down with the power of 1,000 suns with plenty of long-wavelength orange and red light that penetrates deep through the foliage of dense grow room setups. LED lights are unable to compete with HPS lights on this front and are best used in short and wide grow setups with plenty of spacing.
9. Seedling Phase
During the seedling phase, plants require plenty of cool, short-wavelength blue light to encourage growth. This is where LED lights really shine compared to HPS lights, which are much hotter, harsher, and lacking on the blue light spectrum.
10. Vegetative Phase
LED lights emit far more of the blue light required for significant vegetative growth. HID lights can be great for encouraging thick stem and leaf growth during the vegetative phase, but primarily it’s the MH lights used for this purpose and not HPS.
11. Flowering Phase
While it’s true that and LED grow light system can be optimized to emit a ton of red light during the flowering phase, there’s just no beating the pure infrared power that HPS lights produce.
Case in point: This forum thread describes a cannabis grower with a 280 square foot grow space who experimented with an LED setup and got half the yield for twice the cost. That thread is from 2016 and LED technology has been advancing with costs falling, but the overall point still stands.
LED lights will be fine for both thinner crops with less dense foliage and shorter crops, but for plants like cannabis there’s nothing that beats the floral growth production of HPS lights.
LED vs HPS Grow Lights: Final Thoughts
HPS grow lights have been the industry-standard for both commercial and hobby growers for the past several decades because they emit a ton of light that encourages floral growth with huge yields.
But the biggest downsides of HPS lights are some of LED’s biggest strengths:
- LEDs offer high efficiency and long lifespans.
- LEDs run much cooler.
- LEDs emit far more light at the blue end of the spectrum.
Still, many experienced growers are holding off on LEDs for two reasons:
- Costs are still sky-high.
- With some crops (like cannabis) you just can’t beat the yields of that HPS power.
When to choose LED lights
LED lights are best for dedicated growers looking to spent more upfront to invest in lower recurring costs, breaking even over the next 1.5-3 years.
Additionally, LEDs make sense for growers who meet one of these criteria:
- You’re looking to grow non-flowering crops.
- You have a small space with limited overhead and don’t want to risk burning your crops.
- You live in a warm climate where HPS lights would be way too hot.
When to choose HPS lights
HPS lights are best for beginner growers who want to see if growing is for them. If you aren’t 100% sure you’re completely dedicated to growing, it can be tough to stomach the high upfront costs for an LED setup, which really makes its money on the back end.
Additonally, HPS makes sense for growers who meet one of these criteria:
- You’ll be growing dense crops.
- You have a large space with a high ceiling and need the power of HPS.
- Your grow room is naturally cooler and could use the heat HPS lights radiate.
Where do you fall on the LED vs HPS debate? Have you used one (or both) and completely swear by it? Let us know in the comments!