LED grow lights stimulate plant growth by providing an optimized light spectrum specifically to enhance plant metabolic processes.
The best LED grow lights are used the same way as other grow light technologies but provide advantages in luminosity, color temperature and energy efficiency.
Without further ado, let’s jump right into examples of high-quality LED grow lights available on the market today:
|11-band multi-spectrum||Our Review|
|11-band multi-spectrum||Our Review|
|mono-spectrum blue LED||Our Review|
|6-band multi-spectrum||Our Review|
|12-band multi-spectrum||Our Review|
|4-band multi-spectrum||Our Review|
|5-band multi-spectrum||Our Review|
|Multi-spectrum LED arrays and T8 bulbs||Our Review|
Best LED Grow Light Reviews – Our Top Picks
The Diamond Series XML 350 features 10W Cree single-chip LEDs that are the latest in grow light technology. They use blue and white LEDs to achieve nearly total saturation of the red and blue spectrum with 11 light bands to maximize flowering and foliage growth.
Grow bed coverage is optimized by a precision 90-degree collimator lens that has excellent canopy penetration. This series has advanced LED drivers to ensure long LED life, which is further enhanced by dual heat sinks for a 50 percent increase in LED heat dissipation.
Other features include 3-stage color and light intensity settings that are optimized for cloning, foliage growth and flowering stages. Each light has power sockets that permit daisy-chaining up to 4 grow lights on one timer.
Type: This is an 11-band multi-spectrum LED grow light.
- Consumes only 330W to replace up to 1000W HID equivalent
- Excellent red/blue spectrum coverage with 11 bands
- Risk-proof warranties
- 10W Cree XML LEDs make up less than 20 percent of light output
|Dimensions||19″L x 19″W x 3″D|
|Number of LEDs||10 x 10W, 144 x 3W|
|Nominal Wattage||532W||Draws 330W|
|Coverage Area||5′ x 4.5′|
|Special Features||3 spectrum settings||Clone, veg, flower|
To headline this grow light as a 10W Cree LED unit is misleading, since it only uses 10 of those LEDs and fills out the remainder with 144 3W bulbs. That said, Advanced LED Lights has come up with another winning LED grow light that offers high intensity, durability and an impressive money-back guarantee and full replacement 3-year warranty.
They made impressive improvements to the vanilla Diamond Series by beefing up the heat sinks and a 90-degree collimation lens that eliminates stray light away from the grow bed. You can use this light to best advantage over a bed up to 20 square feet. The spectrum setting switch customizes light output for all growth stages from cloning to foliage to flowering.
A welcome improvement over the previous Diamond Series models with rugged heat sinks and more focused light coverage.
Advanced LED Lights’ Diamond Series grow lights come in six different power ranges from 100 watts up to 800 watts. The DS 200 utilizes 100 3-watt Cree high output LEDs that consume 185 watts. The LEDs put out 11 wavelengths that maximize red and blue spectrum that plants need most.
The Diamond Series 200 LED grow light has been third-party tested and proven to produce 79%, 82% and 87% more PAR/W than most competitors at heights of 18, 24, and 36 inches, respectively. Advanced LED Lights provides an industry-leading full money back guarantee within 90 days and a 3-year limited warranty that includes shipping costs.
Type: This is an 11-band multi-spectrum LED grow light.
- Typically consumes only 185W
- 3 color and intensity settings for cloning, veg and flower cycles
- Broad coverage in the red and blue spectrum portions
- High intensity could be a problem if your grow room does not have sufficient height
|Dimensions||5″W x 19″L x 3″D|
|Number of LEDs||100 x 3-watt|
|Coverage Area||3′ x 3.5′|
|Special Features||Color and intensity selection||Veg or flower|
This 200W grow light provides nearly full coverage of red and blue spectrum. There is no UV-B coverage, however, but you can supplement with T5 fluorescents. With 100 3-watt LEDs in this light, they are obviously under-driving them, which probably means they will last. However, you are not getting the full potential of their Cree LEDs. Despite that, users report very high intensity, which is undoubtedly improved by the two-stage lensing that targets the light onto the grow bed. It has a veg/flower, color and intensity switch.
It is hard to find a multi-spectrum light with a 90-day money back guarantee in this price range. The DS-200 is known for deep green foliage and excellent flowering results.
The XT-E series features US-made 5-watt Cree LEDs for a significantly higher level of performance than the original Diamond Series LED grow lights. Each OSRAM LED runs at 3.9W, which is twice as high as other 5W LEDs on the market. With a spectrum concentrated in the blue portion, these lights are extraordinary for producing high vegetative yields. The XT-E lights produce more yield per watt compared to any competitor’s best LED grow lights.
The DS XT-E 200 consumes just 185W, covers up to a 4.5 by 4.5 foot growing bed and comes with Advanced LED Lights’ 90-day hassle-free money back guarantee and 3-year warranty.
Type: This is a mono-spectrum blue LED grow light.
- Optimized for foliage growth with high-intensity blue spectrum
- High efficiency OSRAM LEDs
- Built-in hanger system
- Not a multi-purpose grow light
|Dimensions||8″W x 19″L x 3″D|
|Number of LEDs||40 x 5-watt|
|Multi-Spectrum||No||Blue from 430 to 480nm|
|Coverage Area||Up to 4.5′ x 4.5′ veg mode|
Here is another variation of Advanced LED Lights’ Diamond Series that uses the latest XT-E 5W Cree LEDs that optimize spectrum for vegetative growth only. The intensity of blue spectrum for the same number of watts as a multi-spectrum light means more bang for your buck for veg mode. You also get a generous coverage area up to 4 by 4 feet from a relatively small package and budget price. Couple it with one or more multi-spectrum LED grow lights or red UFO lights and you will have an optimized lighting system that brings faster, fuller yield cycles.
Might be the perfect veg-only light. You get more power efficiency for that grow stage than any other light reviewed.
G8-LED’s 240 Watt model includes 8 bands of LED spectrum plus IR and UV-B coverage. It uses high quality 3-watt chips in a 16 by 8 inch array that produces PAR light equivalent to a 400 Watt HID system. They have achieved an ideal color ratio for efficient foliage and flower production. G8-LED’s lights are all rated for 50,000 hours or a 15-year life span. Circuit boards, power supplies and fans are built to keep the light running cool.
TYPE: Multi-spectrum LED grow light
- High quality components including Zener diode protection
- 8-band spectrum coverage including IR and UV
- 2-year warranty
- Cooling fans are noisy
- They suggest additional 90W Red UFO during flowering
|Dimensions||5″W x 16″L x 2.5″D|
|Number of LEDs||80 x 3-watt|
|Nominal Wattage||240W||Typically consumes under 200W|
|Operating Voltage||110-240VAC||Must specify before shipping|
|Coverage Area||Nominally 6 sq. ft.|
The G8-LED 240W light is compact but packs a punch. HID and fluorescent lighting systems put out a broad spectrum, which makes them appear brighter, but G8-LED has crafted their light to put out the most effective bands of spectrum for veg and flower growth. The IR and UV bands are essential for robust growth.
This light runs cool to the touch. Given the quality of the components and expected lifetime of 15 years or 50,000 hours, their 2-year warranty seems like a piker, but do not let that stop you making this your first LED light. It is perfect for small plots that can be expanded later.
An excellent light for first-time indoor gardeners or those wanting to experiment with LED grow lights. It is the perfect size for a seedling bed.
For larger grow plots, the G8-LED 600 watt LED grow light puts 1000W HID systems to shame. Power consumption is half or less of HID lights while providing exactly the spectrum bands your plants need for optimal growth and flowering. It uses cool running 3-watt LEDs to provide an 8-band spectrum including IR and UV bands.
The G8-600 at 2′ to 3′ above the plant canopy is ideal for a rectangular area of 18 sq. ft. The lower height produces bushy plants. The addition of two 90W red UFOs maximizes flower yields. As always, this grow light contains the high quality diodes, power supplies, fans and Zener protection for which G8-LED is known.
Type: This is a multi-spectrum LED grow light.
- 8-band spectrum with IR and UV is optimized for robust growth
- It exceeds the light power of a 1000W HID system
- Hanging system needs a re-design
- Recommended red UFO light (630-660nm) for flowering is separate
|Dimensions||5″ L x 14″ W x 3″ D|
|Number of LEDs||200 x 3-watt|
|Nominal Wattage||600W||400W typical|
|Coverage Area||18 sq. ft.|
This 600W model from G8-LED is the big brother to their 240W and 450W grow lights. It has the same optimized 8-band spectrum including IR and UV-B that creates deep green foliage growth and excellent flowering. They suggest, however, the addition of two 90W red UFOs in the 630-660nm range to maximize flowering. Those will likely set you back for an additional cost.
You might consider making your own hanging system as the one that comes with this light has apparently not held up well for some users. Be sure to specify your power source configuration because they need to know which plug to send.
Get ready for serious production with this optimized spectrum light. It puts out more growing power than a kilowatt of HID light and runs cool without running up your light bill.
The Extreme 126X-Pro grow light, also known as The Penetrator, uses just 230W to replace an equivalent 600W HID lighting system without heat and ballast problems. It is optimized for a 2′ x 3′ grow area. Its 6-band spectrum outputs wavelengths ideal for foliage and flower production. Light delivery is significantly enhanced by patent pending X2 lenses that increase light intensity over 500 percent compared to no lens. This is HydroGrow’s 3rd-generation lighting system with more energy-efficient, long-lasting LEDs and copper core heat sinks.
Type: This is a 6-band multi-spectrum LED grow light.
- Consumes only 200W but does the job of a 600W HID light
- X2 lenses mean no wasted light outside the grow area
- Can be daisy-chained up to 1200W total
- Fans are rather noisy
- Sharp coverage boundaries may be inconvenient
|Dimensions||5″ L x 12″ W x 3″ D|
|Number of LEDs||126 x 3-watt|
|Nominal Wattage||378W||200W actual|
|Coverage Area||2′ x 3′||2′ above canopy|
|Special Features||3 power settings||1. 5W, 1.0W, 3.0W|
These are well-built grow lights with high light intensity. That is made possible by their X2 lens technology that focuses each module’s spectrum directly on the canopy. The trade-off is that the coverage area is smaller with sharp edges.
These lights’ spectrum is limited to 6 bands but does a good job delivering PAR light compared to an HID or fluorescent grow light. Color spectrum cannot be controlled, but there are 3-power settings from 0.5W up to 3.0W, which allows for light height and growing stage customization. Though HydroGrow is a quality name, the cooling fans seems excessively noisy.
Given the reduced coverage in this power class compared to competitors and only 6-band coverage, it has a high price.
California LightWorks, based in Canoga Park, CA, utilize the latest LED, driver and heat sink technology in all their products. The SolarStorm 440W is powered by energy-efficient 5W LEDs that deliver deep blue and deep red spectrum. The LEDs are supplemented with T8 fluorescent UV-B bulbs for higher potency crops. It provides six bands of spectrum from a compact housing that includes cooling fans. There are three different modes for maximum foliage growth, flowering or high yield flowering. It weighs in at 25 lbs. and comes with a 3-year warranty.
Type: This is a hybrid lighting system that contains multi-spectrum LED arrays and T8 bulbs to enhance UV-B spectrum.
- Consumes 250W in Veg Mode and a maximum of 360W
- Emits high-absorption light bands in blue, red and UV-B spectrum
- Exceeds usable spectrum of a 600W HID system
- Some packages omitted the promised ratcheting hangers
|Dimensions||15″W x 18″L x 5″D|
|Number of LEDs||88 x 5-watt|
|Nominal Wattage||440W||Typically consumes much less|
|Multi-Spectrum||Yes||430-460nm and 650-670nm|
|UV-B||Yes||Two T8 fluorescents|
|Coverage Area||3′ x 3′ flower 4′ x 4′ veg mode|
|Lifespan||50K – 80K hours|
|Special Features||3 spectrum settings|
If you are looking to replace an HPS or MH system of around 600W, give this light a shot. Look for a 50% reduction in electricity cost and zero heat management. It has 3 lighting modes: Veg, Flowering and Flowering+. Depending on light height, your plants receive PAR output from 2,570 down to 832 in a growing area from 3 x 3 feet up to 6 x 6 feet. The additional UV-B T8 bulbs increase bloom.
An excellent light for serious grow light gardeners looking to swap out more costly lighting systems.
The G8-LED 600 watt LED grow light is a 300 watt LED grow light that utilizes 3-watt LEDs precision driven at 650 mA to provide deep canopy penetration. Kind’s proprietary spectrum includes 12 bands total, mostly in the red and blue ends of the visible spectrum, which plants need to flourish and produce maximum flower yields. Kind employs an optical lens to increase PAR light intensity.
Their precision LED drivers and double size heat sinks ensure long LED life without compromising on light output. They use thick aluminum circuit boards to wick away heat. The 300W light only consumes 220W from the outlet, which means these sip electricity compared to hot HID systems.
Type: This is a 12-band multi-spectrum LED grow light.
- Maximizes LED efficiency with precision drivers
- Emits high-absorption 12-band spectrum
- It exceeds the light power of a 600W HID system without the heat
- No UV-B or IR
|Dimensions||15″ L x 11″ W x 3″ D|
|Number of LEDs||90 x 3-watt||15 bulbs per module|
|Nominal Wattage||300W||Typically consumes 220W|
|Multi-Spectrum||Yes||Unique 12-band spectrum|
|Coverage Area||2′ x 3′ nominal||At 18″ recommended height|
|Special Features||High precision LED drivers||Maintains 650 mA|
Kind LED is not as well-known as other manufacturers but that does not mean they do not make a powerful product. They have two significant strengths:
- Whereas many manufacturers simply dial back the LED current to 500 mA and save money using less precise LED drivers, Kind LED drives their LEDs at 650 mA with utmost precision. This approach produces maximum light from every LED while preserving a 50,000 hour life span.
- Their 12-band spectrum is unique in the industry and is proving optimal for heavy foliage growth and maximum flowering.
The K3-L300 uses four cooling fans and the LED circuit board has almost a full inch of aluminum to soak up heat. It is an impressive light that produces great results and runs quietly.
KIND has distinguished itself with a quality light built to last that provides optimized spectrum for veg and flower stages.
This LED grow light is California LightWorks latest model that features high flux 5W LEDs. Forty-four bulbs are arrayed to provide nominal 220W lighting power for grow beds between 2 x 2 to 5 x 5 foot sizes. 80-degree lenses aim light directly at the canopy. Three sub-models are available that offer different spectrum profiles:
- VegMaster – peaks spectrum in both red and blue regions for foliage stages
- FullCycle – Lesser peak in blue, higher in red for general purpose growing
- BloomBooster – Concentrated in red wavelengths to maximize flowering
Up to 10 California LightWorks grow lights can be daisy-chained on a single power cord and timer.
Type: This is a 4-band multi-spectrum LED grow light.
- Consumes only 200W to replace a 400W HPS light
- Three spectrum profiles available for general purpose, flowering and veg stages
- Blue and red spectrum portions narrower than competitors
- You must specify a single spectrum profile at purchase time
|Dimensions||9″ W x 9″ L x 4″ D|
|Number of LEDs||72 x 5-watt|
|Multi-Spectrum||Yes||4 bands plus 3100K white|
|Coverage Area||2′ x 2′ up to 5′ x 5′ for some veg|
|Lifespan||50K – 80K hours|
|Special Features||Available in 3 spectral configurations||VegMaster, FullCycle, BloomBooster|
California LightWorks’s Solar Flare 200W LED grow light is a decent light for its price range. It is the perfect size for closet beds that need to operate on low power with reduced noise. You might question how good the LED drivers are since there are only 2 rated at 100W each, but CLW mitigates that with a generous hood design that dissipates heat quickly with a single, center-mounted fan.
The biggest drawback to these lights is that you cannot get all three spectrum profiles in one light. Each sub-model has a fixed spectrum. You can order the FullCycle and hope for the best, but if you want to optimize veg or flowering you have to order at least one more light.
Good, inexpensive starter LED grow light if you order the FullCycle. For optimization, you need two lights.
With just 265W input, the SOL 6 from HydroGrow easily replaces up to an 800W HPS lighting system with more than twice the energy efficiency and far less heat. It utilizes 6 super-powerful 45W G4 LEDs and a fourth-generation reflective and focusing system for optimum canopy penetration. It is designed to cover a 3′ x 4′ area as primary light but can supplement bed areas up to 12′ x 15′ at a height of six feet.
It produces a 5-band spectrum that emits wavelengths of 440, 470, 525, 640, 660 and 740nm, which super-charge vegetative and flowering stages equally. The patent-pending Fusion Reflector and polycarbonate lens over each LED produce a concentrated light beam without transmission loss.
Type: This is a 5-band multi-spectrum LED grow light.
- Consumes only 265W
- Multi-spectrum light optimized for veg and flower stages
- Each LED has an individual cooling fan
- Since there are fewer lamps, reliability could be an issue if LEDs fail prematurely
|Dimensions||15″W x 18″L x 5″D|
|Number of LEDs||6 x 45-watt|
|Multi-Spectrum||Yes||430-460nm and 650-670nm|
|UV-B||No||Two T8 fluorescents|
|Coverage Area||3′ x 4′ up to 12′ x 15′||Larger space at 6-10′ height|
The HydroGrow Sol6 may be an example of the future of LED grow lights that utilize ever-increasing wattage and power efficiency.
The SOL 6 uses only 6 high-power G4 LEDs as opposed to the dozens on less powerful grow lights. Albeit, it only offers a 5-band spectrum, but as LED lights continue to improve that will not be an issue going forward. These lights are modular and upgradeable. They manage LED heat with thin-finned heat sinks and one dual-bearing cooling fan per LED.
HydroGrow also offers a higher powered model in the same case that uses 85W LEDs. Units can be daisy-chained up to 1200W.
Here is an instance of something new in the best LED grow lights category. With far fewer, but much more powerful LEDs, the SOL 6 provides a modular, upgradeable grow light system.
Why Are They Trendy Right Now?
Indoor LED grow lights are a relatively new technology. As a consequence, they have obtained the new-kid-on-the-block aura. Furthermore, the trend towards legalization of cannabis has raised awareness of indoor grow light systems at precisely the time when the best LED grow lights are proving themselves superior to older technologies. Plus, they are ideal for first-time growers.
Existing LED grow light companies and start-ups are ramping up their product lines to meet the new demand. All of this activity creates a storm of chatter on the web about the latest grow light improvements, especially in LED grow light reviews.
Before running off to the local hydroponic shop or online retailer, you should learn the differences between cheap LED grow lights, the top LED grow lights and those in between. Do not be tempted by the cheapest LED grow lights as they will likely disappoint. This guide outlines what are the best LED grow lights and the features that meet particular growing needs.
Why Should You Invest in LED Grow Lights?
There are various reasons why it’s a nice idea to invest into LED grow light. Check out most important aspects:
Replacing the Sun’s Rays
The point of grow lights is to replace the natural sunlight that plants would receive outdoors. Plants must have light to flourish, but for the processes of photosynthesis that combine CO2 and water to create sugars and oxygen, not all wavelengths of sunlight are created equally.
The highest rate of photosynthesis is provided primarily by orange and red lights and secondarily by blue-violet light. The majority of green spectrum is reflected, which gives plants their pleasing green color. Fortunately, the best LED grow lights can fine-tune their spectrum emission to optimize for any plant you want to grow at its current stage of growth.
LEDs are the most efficient method of converting electricity to light in the human visible spectrum. Applied to grow lights, they also save energy by reducing wasteful spectrum emission not required for plant metabolism. Later in this guide, you will find LED grow light reviews that discuss spectrum profiles.
Unlike indoor grow lights such as metal halide grow lights that rely on one or a few output bulbs, LED lighting uses dozens of lamps. If a few LEDs fail or dim in a large array, little light is lost as a result.
Quality LEDs have a far greater average lifespan than other lights and fade little over that lifespan. The normal lifespan of an LED exceeds 50,000 hours as compared to a metal halide light that loses 50 percent of its brightness well before 10,000 hours of operation. As LEDs near their end of life, they are still producing 70% light output.
All lighting technologies produce waste heat. For lamps other than LEDs, this heat is directed at the plants. This excess heat may have adverse effects if not channeled away. The minimal heat from LEDs is directed in the opposite direction of the light they emit and heat sinks easily wick it away.
LED lighting, also known as solid-state lighting, requires no vacuum tubes, special gases or a filament to produce light. Different base materials primed with special impurities can be used to customize the wavelengths of light an LED produces. These impurities include tellurium, germanium, silicon, zinc and nitrogen among others.
Costs Trending Lower
You may have heard of “Moore’s Law” regarding the doubling of transistors on a CPU chip every 18 to 24 months. For LEDs, there is an analogous law known as Haitz’s Law. It states that the cost per unit of useful light is reduced 90% and the light produced by an LED increases 20-fold for each decade. This is why LEDs continue to increase in efficiency and their purchase costs continue to decline.
According to the International Energy Agency, lighting consumes nearly 20 percent of total electricity demand around the globe. This amount is equal to 70 percent of the CO2 produced by all the world’s cars. Most of this light is produced by inefficient incandescent bulbs and non-LED lighting technologies. Unlike HID or fluorescent lights, LEDs do not contain mercury.
What Are Lumens and How Many Do You Need?
It used to be when household lights were incandescent that you could measure the brightness of a lamp by comparing lamp wattage. With so many types of lighting technologies of varying efficiency that measure is obsolete. Watts is an especially misleading measure of light output for incandescent bulbs that produce a lot of waste heat. Furthermore, much of their light is outside the spectrum visible to humans.
Watts vs. Lumens
The de facto standard for comparing lamps is now the lumen, which measures the actual amount of visible light a lamp produces. To compare efficiencies between lighting technologies, the accepted measure is the number of lumens produced per watt of energy input, or lm/W.
Amount of Light Needed by Plants
Unfortunately, when it comes to comparing grow light technologies, lm/W is only part of the story, since some wavelengths within the visible spectrum are more important to plants than others. Wavelength is measured in nanometers, which is abbreviated nm.
You can learn about the amount of light needed for your plants in this video:
Light Sensitivity between Plants and Animals
In their perception of the visible portion of the light spectrum, humans and plants naturally differ. The human eye has a variable sensitivity to colored light that diminishes at the red and blue ends of the spectrum and is highest in the center where green light is seen. Plants have an almost mirrored perception of this spectrum.
Light Bands Used by Plants
Since plant light requirements are tied to specific metabolic processes, their light sensitivity has distinct peaks across
the spectrum. For example, the main workhorse of photosynthesis, chlorophyll a, has absorption peaks at wavelengths of 430nm and 662-700nm. Its close companion, chlorophyll b, has peak absorption at 453nm and 642-680nm.
Phytochromes are plant pigments that measure the amount of light reaching the leaves. These help regulate how fast leaves grow. They have their own absorption peaks.
Scientists have discovered that other wavelengths in the orange and blue-violet sections of the visible light spectrum also have important roles to play as does Ultraviolet-B. The combinations of different wavelengths and their ratios are necessary for healthy plant growth. Read LED grow light reviews carefully to see which portions of spectrum are provided by a particular grow light.
If Not Lumens, Then What?
Simply using lumens as the measure of a grow light’s spectrum efficiency is not adequate. Instead, what many of the best LED grow light manufacturers rely on is the number of lumens of photosynthetically active radiation or PAR light.
Unfortunately, you will not find this standard applied uniformly among those who sell grow lights of any technology. Many claim in LED grow light reviews that plants need a full spectrum of light and thus PAR is irrelevant. As we have seen, however, plants can thrive quite well without a full spectrum.
The specific portions of spectrum provided is one factor that helps distinguish between cheap LED grow lights and more effective ones. Later, spectrum profiles will make clear why LEDs make the best grow lights for any crop whether it be lettuce, tomatoes or cannabis.
What Are Cree LED Grow Lights?
Cree LED grow lights are not a brand. The term refers to the LEDs themselves. They are simply the highest quality, most efficient and reliable LEDs made.
They approach 120 raw lm/W, do not fade significantly and can easily exceed an 80,000 hour lifespan. LED grow light reviews do not always call out if the LEDs are Cree or not, so shop carefully.
Comparison of Grow Light Technologies
HID vs LED
Included in High-Intensity Discharge lighting are Metal Halide and High-Pressure Sodium lights. Both are similar with regard to spectrum output, heat and maintenance costs, so they can be discussed together.
Regardless if MH or HPS lamps are used, compared to LED lighting they have a number of deficiencies. They are hot, so need higher placement. They require reflectors, a ballast, a hood and heat venting. These latter items are often overlooked in LED grow light reviews. Both MH and HPS produce an adequate growing spectrum and spectrum not required for growing, which energy is lost.
- MH is full spectrum but higher in blue/green
- HPS is full spectrum but higher in yellow/orange
- Heat waste is useful during colder weather
- Theoretical 20,000 hour lifespan
- Excess spectrum wastes energy
- Omni-directional beam pattern wastes light
- Extra heat management costs
- Plants require more watering
- Long start-up/cool down cycles
- 50 percent lumen loss at 10,000 hours with no reduction in consumed power
- Frequent bulb and ballast changes
- Glass envelope blocks UV-B
Fluorescent vs LED
Fluorescent lighting has recently improved due to T5 High Output bulbs. These are significantly more energy efficient and cooler than the standard T8 bulb. A T5 contains a mixture of mercury vapor along with an inert gas such as neon, argon or krypton. There are two different spectrum intensities, warm or cool white.
- Lowest initial cost across lighting technologies
- Lifespan around 10,000 hours with 5 percent luminosity loss
- Run cooler than HPS or MH
- Can be placed closer to plants
- Can mix light colors to cover red and blue spectrum ends
- Supplemental UV-B tubes available
- Require ballast and reflective hood
- Less energy efficient than LEDs long-term
- Mercury in bulbs is hazardous waste
Induction versus LED
The induction lamp was invented by Nikolai Tesla in 1891 and it is still one of the most reliable and energy efficient sources of light. They have fewer parts to fail, run cool and produce a broad light spectrum. They are sometimes referred to as plasma lights.
- Spectrum ideal for leaf growth
- 100,000 hour lifespan with minor degradation of output
- Substantially cooler than HID lamps
- Spectrum includes UV-B
- Instant On-Off and dimmable
- High initial cost
- Needs supplemental lighting for flowering stages
When comparing the costs of grow light technologies there are three factors to consider:
- Initial cost of bulbs and fixtures
- Replacement costs of bulbs and ballasts
- Ongoing energy costs
The estimates below assume a 4′ by 4′ grow area and an average 16/8 hour cycle time, which accounts for both vegetation and flowering cycles. Cost of electricity is assumed to be 12 cents per kilowatt-hour. The replacement cost for HID includes a new ballast as recommended by most repair technicians.
Not included is the cost of heat management equipment that may be required for HPS, MH or fluorescent lighting systems.
|T5 HO Fluorescent||HID||Induction||LED|
|Fixture||12 – 4′ T5 HO 54W bulbs||AquaLight 400W HID Kit||Inda-Gro 420-PAR||HydroGrow Extreme 126X|
|Annual Bulb Cost||$112||$172||N/A||N/A|
|8-year Total Cost||$3870||$4066||$3152||$2796|
|Notes||Ballast replacement included||70K hours life span||50K+ hours life span|
Even though an LED system may cost more than other lighting technologies initially, in the long run it more than pays for itself especially as energy costs rise.
Furthermore, keep in mind that LED lighting technology is the only one of the above four that is continuing to improve at an exponential rate in its light to power ratio and spectrum customization.
The Secrets of Successful Growing
Light to Plant Distance
There are several factors that determine the optimal distance between grow lights and the plants upon which they shine:
- The amount of PAR lumens given off by the light
- The amount of heat given off by the light
- The stage of growth of the plants
- The types of plants being grown
Once you combine all these factors, you may feel that setting the proper height for your grow lights is more art than science. Educated guidelines and height ranges are given here, but these should be modified according to experience.
The Inverse Square Law
The amount of light or lumens shining on a fixed area is inversely proportional to the square of the distance between that area and the light source. Thus, as you move a light source away from your plants, the amount of light reaching the plants drops dramatically. For instance, if 100 lumens are hitting a square foot of plants when the light is 1 foot away, then at 2 feet, only 10 lumens will reach those plants.
Therefore, you want the light as close as possible in order to maximize the lumens each plant receives.
However, there are additional factors to consider.
Except for induction and the best LED grow lights, other technologies emit substantial heat. Up to a point, this can benefit plant growth, but too much is detrimental. You have a lot more leeway with LED or induction lamps in that regard.
Too Much of a Good Thing
Too much light triggers a process known as photoinhibition that acts as a governor on metabolic processes. Too much light can stunt, damage or kill plants.
Stage of Growth
Placing lights too close to sprouting seedlings usually inhibits root growth, which is critical at early stages. Seedlings can dry out excessively, which leads to stress. It is better to raise the light until foliage growth is well under way and then lower it 2″ per week to an optimum height.
The guidelines for both the number of hours a day your plants should be illuminated and the light distance also depend on whether plants are in a foliage or flowering stage. For cannabis plants, up to 24 hours a day of light is beneficial during the first months for robust foliage. Later, that time should be cranked back to 12 hours per day to induce flowering.
Guidelines for Lamp Height by Light Type
In the table below, all lamp types are approximately normalized to match a 400W and 1000W HID light. These height ranges are recommended for plants beyond the seedling stage.
|Lamp Type||400W HID equivalent||1000W HID equivalent||Notes|
|Metal Halide||5 – 18 inches||9 – 31 inches||Watch heat at canopy|
|HPS||6 – 20 inches||10 – 36 inches||Watch heat at canopy|
|T50 HO 8 and 20 bulbs||6 – 18 inches||10 – 26 inches||Heat less of a problem|
|Induction||6 – 12 inches||8 – 24 inches||Negligible heat|
|LED 240W and 600W||6 – 12 inches||8 – 24 inches||Negligible heat|
When setting the initial height and making changes, be sure to monitor your plants closely for stress or drying and adjust accordingly. Often, you can find guidance in LED grow light reviews for your particular grow light.
Light Cycles and Why You Should Care
Plant species are like individuals. They have their own preferences for full sun or shade, but in general follow these steps with regard to the daily light duration whether you grow veggies or herbs:
- During germination and sprouting, give light 24 hours a day. Mind the distance from the seedlings, especially if you are using HID or fluorescent lights.
- Once seedlings have several leaves, reduce light time over two weeks until you reach a 16/8 ratio. This is still enough to stimulate foliage growth.
- Once you are ready to induce flowering, reduce the light duration further to a 12/12 ratio.
If your plants do not respond as expected to the light cycles you are providing, there are a couple of adjustments you may make:
- Photosynthesis has an upper temperature limit after which it becomes less efficient or shuts down. To mitigate this, try flipping the light cycle so that the lights are on during cooler nighttime temperatures.
- The best LED grow lights allow you to shift spectrum toward the blue end for vegetative growth and toward red during flowering.
Once you get the hang of plant light cycles, you can use them in reverse also. You can induce more vegetation any time by increasing light duration for example.
Watch the video below to know more details about grow lighting:
The Future of Grow Lights
If you remember Haitz’s Law, you recall that LEDs are on an exponential growth path for energy and light producing efficiency. Every 10 years, cost per lumen is 10 percent of what it was at the start of the decade. Additionally, the amount of light produced is 20 times greater. Haitz’s Law shows no signs of abating.
The best LED grow lights have already overtaken other lighting technologies and improvements are coming fast, so you could say that the future of grow light technology is already here. Other technologies, such as fluorescent and induction lighting make incremental improvements, but they cannot keep up with LEDs.