LED vs. HPS and HID Grow Lights - 2017 Edition

LED vs. HPS and HID Grow Lights - 2017 Edition

Many fans of HID and HPS lights have resisted or rejected the new technological uprising of the LED. Yet, time and technology stop for no man and LED advances have soldiered on despite the less than total following. The demand for better, brighter, and bolder has pushed the technology of man-made light to a modern and very bright pinnacle.

Could there finally be a lighting system that meets every ideal of a stellar indoor grow? Finding the answer has taken deep consideration of cost, draw on energy, efficiency, and purpose, not to mention the engineering design and lumen output of each option.

We are on our feet with bated breath because 2017 has brought us to what seems like a closed gap in the race between HID / HPS and LED if not a new leader. Is there a clearly better lamp? Let’s take a look.


High-Intensity Discharge

High-Intensity Discharge (HID) bulbs have ruled the landscape of horticultural lighting for ages. They were initially known as gas discharge lamps. They would emanate light as metallic salts inside the electric arc chamber became heated to the point of being vaporized.


History of lighting

For centuries scientists have worked with glass tubes, gasses, metals, and electricity to fine tune the combinations that yield a glowing reaction.

Horticulture’s progress has been well lit by HIDs of all sorts. Gas lamps invented in the early 1700s evolved steadily and rightly established their place as a dominating technology.


These days, HID refers to a handful of gas lamps including High and Low Pressure Sodium (HPS), Mercury Vapor (MV), and Metal Halide (MH).


It’s a broad spectrum of abundant light that gives the HID the ability to mimic the sun’s rays well enough to effectively grow plants.


Until today HID technology has prevailed within the indoor horticulture niche. They have brought forth beautiful results along with huge draws on energy.


Fortunately for the grower, a new leader is on the horizon.

Light Emitting Diode

Today, more efficient LED technology is pushing HIDs out of their well earned and long held place at the head of the pack. The LED is fast making strides to become the indoor horticulturists’ new best friend. As improvements offer a whole new level of growing to explore, it is easy to imagine a whole new wonderful world of growing possibilities.  

Modern Advances

The effects of the spectral science and discoveries within the horticulture niche demonstrate fantastic advances. Using light to create more robust yields with better flavor is just the tip of the benefits iceberg. Other advantages include cost savings, light efficiency, cooler running, and spectral stability.

Cost Analysis

In a world of consumerism, and cost benefit analysis, the almighty dollar is the hinge upon which even lighting decisions are partially made. In a comparison of HID vs. LED costs we look first at installation, then maintenance, and life expectancy.



No matter which fixture you opt for there is a cost to acquire and assemble all the components into place. Comparing HID to LEDs demonstrate similar set up costs to install. However, using HID lamps also requires a ballast, a reflector, duct work, ventilation, and air conditioning. Operating these fixtures consumes a great deal of electricity that ultimately comes at a loss of profit for the grower.

One way to curb installation costs can work for any type of lighting set-up-

Use fewer fixtures with higher wattage in each.  



Once your fixtures are installed properly, maintenance then becomes tied mostly to the life expectancy of whichever fixture you have set into place.

Life expectancy

Myriad options abound when selecting HID lamps and they greatly vary in life expectancy. What is now most recommended is the double-ended HPS lamps which perform best in comparison to other HIDs.


Presently, the most widely used double-ended HPS lamps are expected to function with minimal spectral variance through 10,000 hours.


Once the light begins to degrade, the cost to replace that lamp would be about $140. You can expect to replace bulbs at least once per year. The cost of electricity to power HPS lamps comes to about $600 per year.

Similarly operated and utilized LEDs with equal wattage have a lifespan of closer to 50,000 hours. Age does not seem to alter the spectral output of an LED.


LEDs life can be extended by cooler running and ambient temperatures. The many factors that contribute to the temperature of LEDs alter their cost efficiency over time.

Buyer Beware


The measure of replacement cost depends so much upon the quality of the purchase that it is hard to quantify a simple answer. The highest quality LED light systems come at a premium but can be well worth their initial cost and last an entire decade of very regular use.


Improvements continue as technology rapidly advances in this area. We can look forward to the cost of LEDs coming down in time.    


The comparative qualities of the HID and LED demonstrate clear advantages in a number of performance categories.


Lumens per Watt- Light Efficiency

A measure of energy savings can be substantial when LEDs are used instead of HIDs.

To measure this efficiency we factor in a few things. One factor is the lumens of HIDs compared to the candela of LEDs. The words are different but the idea is the same.

Commonly, lumens per watt divides the amount of light produced by the energy required to drive the function of that mechanism.

At the outset, both LEDs and HID sources appear similarly efficient with a yield of more than 100 lumens/watt.

That is great, but if we leave it there, we are missing our objective. Instead, we want to know how many lumens actually reach the targeted area- the canopy of hungry photosynthesis receptors among layers of leaves in a grow area.

Taking this into account, we have to adjust for the additional factors that dilute the energy actually reaching plants.


Reflection Reduction

Traditional HIDs have the benefit of being very efficient in terms of their output of photons per joule of incoming energy.   However, if we turn the discussion over to how well that efficiently created light is able to get to where it needs to be absorbed by the plant, the efficiency is lost. Energy inefficiently travels from the ballast to the bulb to the plant without use of an additional fixture to act as a reflector.

Unfortunately, even reflectors at their best absorb a full 5% of the light energy meant for the plants. Many subsequent reflections further dissipate the light, drain efficiency, and ultimately the canopy is only presented with 85% or less of the overall initial output.

The benefit of LEDs over HID lamps in this area comes from the lack of need for any reflectors because the lights themselves are directional. They are unlimited by the extra materials that absorb and only partially reflect the light.


Diminished Quality + Altered Spectrum = Frequent Replacement

The normal operation of HID lamps degrades steadily over the first year of operation (and beyond)to a loss of up to 15%.

Not only do they quickly lose quality, the light spectrum of the HID actually shifts away from the most utilized colors (e.g., blue, red, and white) into a yellow-green range that is less useful in a cannabis grow.  

Those HID lamps also designed to feature a dimmer tend to have the most change within the spectrum. It is best to avoid these lamps altogether for horticultural applications.


For indoor gardeners looking to get the very best output from their HID lamps, frequent replacement is the only way to keep the spectrum offered consistent as well as the lumen output high.

Replacement quickly adds a significant cost to running an operation reliant upon HID lamps that cost between $50-$70 each. Experienced growers lean toward replacing single end HID bulbs every 6,000 hours to ensure the maximum output from their lights. At the least, this comes to each year and a half.

Double end bulbs out live their predecessor and remain 90% efficient through 10,000 hours. But the most modern technology that exists and flourishes in indoor horticultural markets revolves entirely around LEDs.

LEDs demonstrate less than a tenth in output decrease and maintain an unwavering spectrum. These qualities may extend beyond a 50,000 hour lifespan.

Excessive Heat and Infra-Red Radiation Cooling Costs

A traditional HID depletes up to 95% of its energy in the form of heat or radiation. And though LEDs run cooler, they are not without heat.

The amount of heat HIDs generate means they need to remain at least a couple feet above the canopy greatly reducing the amount of light available to the plants. LEDs on the other hand can be kept as close as a foot away allowing the light to be directed just where it’s wanted.

Operating temperatures have a direct correlation to efficiency. At 400 degrees Celsius the lamp is not only very hot, becomes less efficient, but is also a source of Infra-Red radiation which can cause damage from heat stress among other things.

Without employing proper cooling and conditioning techniques and running ventilation systems during light hours, reduced performance and fire become definite risks to the indoor grow. Take safety precautions.


Temperature control is an essential element within a lighting system that best retains the quality of lights you use.  

  • The heat coming from an LED is half that of a comparable HID.
  • Heat is transferred away from the plants from the back an LED circuit board into heat sinks where heat dissipates.  
  • LEDs are often referred to as “cool”.
  • No infrared radiation is emitted from an LED’s spectral output.

Temperature control maintains the life and output of the LED. Allow for sufficient means for moving heat away from all light systems for best performance and safety.

Overall, when you take into consideration the losses in efficiency caused by trapped light, absorbed light, ballasts, and operating temperature, an HID lamp system yields 30 lumens per watt.

Comparatively, LED losses come primarily through power drivers and operating temperatures. Their efficiency remains above 50 lumens per watt demonstrating better overall light emitting performance.

HID vs. LED Plant Performance

Plants create cells by combining light energy with carbon molecules from our atmosphere, hydrogen pulled from water, and minerals from earth.

Within these plant cells are pigments that serve to harness fuel for the plant and absorb light energy. The green color we identify with plants in particular comes from their most prolific pigment-Chlorophyll. It is chlorophyll that drives the photosynthesis machine within a plant.  

Quality or Quantity?

Many claims have been made on the premise that spectral distribution is a contributing factor in increased plant growth. How light affects photosynthesis can be seen demonstrated on the Yield Photon Flux curve. This shows how significantly more photosynthesis results from red and orange photons over blue

or cyan ones and relates to the PAR value. PAR stands for photosynthetically active radiation. This translates to how much light is actually available for the use of the plant.

The higher PAR value the greater the quantity of light available for photosynthesis.

Photosynthesis Along the Spectrum

There are various forms of chlorophyll that each readily absorb light energy across spectrums.

Chlorophyll A is what takes in the the violet, blue, orange and red spectrum in particular. Chlorophyll B takes up the violet, blue closer to green, and orange in addition to red.

However, rather than being absorbed, when light in the yellow or green spectrum is available, the plants reflect most of it back. That reflected green light what makes plants appear green.

Along the spectrum are ranges that can still be absorbed by the underside of leaves where reflected light reaches after being bounced around.  

Ideal Ranges

It would seem logical to imagine that the best light would be one that most closely mimics the sun’s full spectrum of light wavelengths. The most abundantly accessible light from our sun comes from the green, yellow, and orange range. However, as growers our focus is on getting the most active photosynthesis feeding our plants. That activity is at its greatest within the blue and red frequencies.

At different stages of growth a plant requires different wavelengths of light to optimize unique functions. Lighting technology has created the opportunity to simply and easily alter light systems to create a shift in the spectrum of light we provide to our plants.

Controlling the light spectrum without changing fixtures
is now a reality in the hands of the grower.

Light Physics

It’s also important to keep in mind that light follows the inverse square law. As light moves away from the source it becomes exponentially weaker. Light at 2 feet from the source is 4 times weaker, whereas, light at a distance of 3 feet is 9 times weaker, and so on.
Plants can only tolerate being up close and personal when they aren’t being burned. Cool running LEDs make that a possibility.


High-Pressure Sodium

HPS lamps are HID lights. In these lamps electricity flows through a glass tube filled with a mixture of sodium, mercury vapor, and xenon gas to result in a light high in the orange/red spectrum.  

Newer double ended lamps with more pressure are nearing an even more red wavelength than the majority that rest where plants are less able to utilize it.

These lights are useful during the budding and flowering stages of cannabis growth but need to be used with caution. High heat can damage leaf tips and buds unless placed at a safe distance.

Metal Halide

Similar to HPS bulbs, Metal Halides are also HIDs. They differ in that they also contain individual metal halides of bromine or iodine that produce green, blue, and red wavelengths.

When heated these halides emit light from the gas that is created. This allows for a blended spectrum which sounds great at the outset but is inefficient. Of the 3 colors, reds are the most short-lived. Even at their best they still offer minimal amounts of the red spectrum that is so desired in a grow. Therefore, Metal Halide lamps are generally useful for the vegetation stages of growth where the green spectrum is ideal.

Much unlike the unbalanced and inefficient halides that offer different spectrums but degrade, LEDs can be designed to meet individual needs specific to a plant’s life stage. A light spectrum in the vegetation stage can easily be switched to a flowering stage spectrum once it is time.

LED Technology

Like a steady stream of nutrients fed through a drip line, the narrow spectrum bands produced by LED chips can deliver a precise blend of spectral light. A grower who knows well what their plants light needs and reactions will be can tailor the light for maximum utilization and absorption.

Beyond the ability to efficiently deliver precise light requirements is the benefit of LEDs being

able to do it all using 30-40% less power. By operating lights at a low temperature there is a reduction in cooling costs as well as watering.

While LED technology is yet new, many manufactures have products they make all sorts of claims about. Before you purchase be sure you are sourcing from a reputable company with a proven track record.


White LEDs

White LEDs. These are the most expensive LEDs. What they offer in PAR comes closest to the broad sunlight-like spectrum that helps achieve the highest quality grow.  

This design uses 4 spectrum bands that align well with the 4 Chlorophyll peaks, along with a portion of light being provided by LEDs with phosphors.   A third of white LED light comes from the a spectrum of green to yellow wavelengths that are absorbed by the carotenoids of the plant.

Though no LED is truly white, packages that combine a red, green, and blue chip together in one LED mix to create white looking light. These combinations are flawed as of yet because green LEDs are inefficient and expensive. Instead, many “white” LEDs are made of both a blue LED chip with a phosphors coated lens. In effect, this hybrid becomes a small LED light powered fluorescent.

Blue LEDs are the most efficient of all available LEDs. Using all three color spectrums to make the white brings the efficiency to lie right between the red and the blue.   To make them truly white they still must offer enough green spectrum light as well. Overall, white LEDs are best utilized during the vegetation stage alone.

No matter which LED you opt for, always consider the spectrum it covers and how available that light is to the plant as designated by the lamps’ PAR value.

Hybrid Spectrum LED’s

We have seen a number of options best suited for the vegetative stages of growth. When it comes to growing cannabis, the vegetative stages are foundational to developing support for the ultimate goal of flower growth. An adapted design that brings LEDs into a configuration and delivery system that works best for flowering as well as vegetation is called a Hybrid Spectrum.


Developing the technology that can dose plants with the exact light wavelengths needed to support this lead to the discovery that we can in effect, design a plant with light. This is known

as photomorphogenesis. Plant characteristics such as size, shape, and compound ratios are beginning to drive the direction of LED hybrids.

The shade stretch response has been adequately researched and is understood to be a reaction to the ratio of far red to red light. One other well studied example is that of the long and short day flower response that triggers flowering.

Manipulating light provides the signals that trigger different responses. While there is more to learn, it is clear that in general a greater percentage of red light leads to stem and flower growth, while blue light boosts pigmentation, terpene production, as well as leaf and resin development.

Indoor and outdoor cannabis grows result in more and less dense buds respectively. This greatly affects the market value of the finished product. Sunlight has a higher blue to red ratio than HPS. LEDs are able to be customized to simulate more closely the light of the sun and therefore achieve the more cosmetically appealing buds. Being able to switch to a more blue spectrum at the touch of a switch makes an ideal way to customize through the last couple weeks of ripening.



Ripening leads me to the last and most exciting benefit of using LEDs. If there is one thing every grower wants, it’s more for their money. The tests have been done and conclusions have been made.

According to Delilah Butterfield of Herb 28 November, 2016, “A 600w HPS light can produce up to 150 to 300 grams in optimal grow environments, which is 0.5 grams per watt or less. LEDs, however, can produce as high as 1 to 1.5 grams per watt.”

The case for LEDs can even stand on this reason alone!


2017 Best of the Best

Now you know that there are excellent options for growing smarter by utilizing the most current lighting technology available to indoor growers. No matter which LED you opt for, always consider the spectrum it covers and how available that light is to the plant as designated by the lamps’ PAR value.

The top LED manufacturers share some commonalities and technology that have officially blown HIDs out of the water. What you find of each are precision crafted and purposely driven LED sequences designed to suit the specific light requirements of chlorophyll A and B in cannabis plants.

The lifespan of these diodes often exceeds 50,000 hours of intermittent use. The customizable spectrum of light these offer are useful through both the vegetative and flowering stages of plant growth.

The LEDs of today are safe, simple, and truly easy to use. Research and developments continue to reach further and create more beautiful products that serve to simplify the indoor gardener’s job.

Still, the initial investment is high. If you are a small scale grower looking to keep costs at a minimum while you get started- HPS HIDs still remain a solid and worthy option.

If you are ready to jump in with both feet, well researched light systems are available from lots of reputable sources both online and in specialty grow shops. Get yourself started with a new LED system and take your indoor growing experience to a new high!

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  • Aston Reynolds
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