The Best LED Grow Lights

the best led grow lights

Light emitting diodes (LEDs) are sources of light produced after a current passes through a microchip. To avoid excessive heat damaging the components, a heat sink is installed to divert it away and increase the survival rate of the LED.

The light from LEDs can be focused in the direction needed to maximize plant growth, reducing the money you have to spend on reflectors. Couple that with huge efficiency savings and it's easy to understand how LEDs have quickly become popular in the hydroponics community.

LED Efficiency

When we refer to the efficiency of lights we’re talking about the amount of photosynthetically active radiation (photons) produced per joule, which is shortened to (µmol/j). One micromole is 602,000,000,000,000,000 photons and a joule is a watt of electrical energy consumed per minute.

So the higher the number is, the more photons are being sent out per the cost of your electrical bill. Even more simply, the higher the number, the less you pay for your plants to grow.

The survival rate is the lifetime of the lighting unit. The fantastic thing about LEDs is the number of hours they’ll last without having to replace them. Your typical LED unit is going to last a minimum of 30,000 hours. If we break it down to more manageable figures because we are but human. A year has 8760 hours in it, so, 30,000/8760 = 3.42 years of use before you’ll even need to think about buying a new one.

Correlated Color Temperature

The correlated color temperature (CCT) of light is measured in Kelvin and is the color appearance of white light. Warmer color is around 2700K, neutral white is 4000K and cool white is 5000K plus.

The general consensus is lower Kelvin, producing red light, is ideal for flowering and higher Kelvin, bluer light, is great for stem growth. Look, we don’t believe this. At least, not to the extent some people in the community emphasize it. Do your own research but it feels like a gimmick. We didn’t find anything even close to a reputable source on this information. The majority of the science came from forum posts and not from peer-reviewed journals.

We’ve added it to our table because it remains an important factor for a lot of people and we don’t want to exclude the data our readers want. If anyone wants to put the record straight, we’re all ears.

LED Colour Rendering Index (CRI) rating

Color rendering index (CRI) is a measurement which ranges from 0% to 100% and describes how well a light source can illuminate an object’s true colors. The higher the percentage, the superior the light source is at color rendering. CRI isn’t an indication of a light source’s color, but how well it can illuminate another body’s color. If a bulb has a low CRI percentage, some colors on the object being lit may look unnatural.

The Lighting Research Center states the CRI rating of 95% for incandescent lamps (which are the classic home bulbs with wire filaments heated to the point of glowing). Cool white fluorescent bulbs have a value of 62% unless they contain phosphors which can bring it up to 80% and above. LEDs are so popular because they have CRI percentages typically over 80% - here, Yuji claims their LEDs produce CRI ratings of 98% which suggests an ever growing confidence in the technology. Gone are the days of purple or orange hue distortions and now people are more willing to use LEDs in their homes as the color disruption is minimal.

Chart of CRI rating by various lighting types

Source

Photosynthetic Photon Flux

Photosynthetic photon flux (PPF) is the number of photons released by a light source per second in a given area within the photosynthetic wavelength range. It’s expressed as micromoles/second or µmol/second and is important because it measures how much potential energy your plant could absorb from the light.

Photosynthetic Photon Flux Density

The photosynthetic photon flux density (PPFD) measures the actual number of photons arriving at your plant’s leaves every second. Again, this is within the wavelength range necessary for photosynthesis and is recorded as micromoles/square metre/second or µmol/㎡/second

the cost of led lights

The initial cost of the LEDs is high. Having said that, it’s worth spending the money if you can. You’re not going to be changing the bulbs for 30,000 to 60,000 hours and their efficiency means you save your money in the long run.

High-pressure sodium or metal halide bulbs may cost less but they’ll destroy your electric bill. You’ll be spending the majority of your time desperately cooling your grow tent down so your plants don’t wilt off and die.

LED heat

COB LEDs are efficient, of that there’s no doubt. They still run on electricity though, and heat buildup remains a possibility, so much so the circuits can fail as a result.

Heat sinks are used to dissipate excess heat to the air and away from the diodes. They come in a variety of forms but each type has a high surface area for as much heat exchange as possible.

Each sink is either active or passive. Active heat sinks have air blown at them to speed the heat dissipation up, meaning you can run you COB LEDs with more power and smaller units. They’re similar to the fan running in your PC or laptop, preventing it from overheating. The danger is your fans breaking, raising the temperature of the unit and destroying your LEDs. Passive heat sinks are simply the heat sink metal working on its own, not as efficient but designed to be able to do the job without intervention from you.

LED Drivers explained

Thermal runaway is when an increase in temperature causes a change in the conducting material leading it to draw more power and become even hotter. This can’t continue as the circuit will destroy itself.

Combatting this requires a driver. An LED driver controls the amount of electrical power reaching the unit by matching its output with the LED’s properties. There are two main types - low voltage DC input power and high voltage AC input power, which are called off-line drivers. The typical recommendation is to use a low voltage DC input power driver, even with higher AC input as you can convert the power supply to DC for compatibility.

If you want your LED to fluctuate in intensity, you need a dimmable driver. It’s beneficial because you can lower the power going to the module and bring the fixture closer to the plants. This way you save money on the electricity bill by being more efficient with your photons. It’s essential you find out the current your COB LED works at. The higher the current, the brighter the light emissions and the higher the wattage.

The number of LEDs which can be run on a single driver is worked out by dividing the maximum output voltage of the driver by the forward voltage of all the LEDs which’ll be drawing power from it. The maximum output voltage is worked out by subtracting the voltage needed for the driver circuitry to function, around two volts.

new led technology

Fluence Bioegineering are a firm which specialises in manufacturing equipment necessary for advanced growing of plants.

In 2016, researchers at the Rutgers University and Utah State University concluded and confirmed the VYPRx PLUS, developed by Fluence Bioengineering, had a 21 percent and 58 percent increased efficacy than the best 1000-watt double ended and single-ended high pressure sodium (HPS) fixtures, respectively.

Moreover, the VYPRx PLUS was better than the leading LED technologies as reviewed in the scientific report analysing the economic effects of greenhouse lighting by Nelson and Bugbee, 2014.

They recorded the efficiency of the unit to be 2.05µmol/j, typically lighting is deemed highly efficient if it’s around the 1.5µmol/j, however, this number is increasing as technology improves. In fact, this was only the second LED fixture the researchers had investigated at the time which produced results above 2.00µmol/j.

COB LED grow lights

In 2016, there was a report conducted detailing the global LED industry demand and supply. The two most popular COB LED manufacturers on the market today are Cree, and Citizen as demonstrated by their share of the total revenue. After these, Sharp and Bridgelux were joint third.

Cree’s most popular models are the CXB3070 and the CXB3590 with the CXB3590 being the best lighting option. The CXB3070 is slightly cheaper but not as effective at growing your plants.

During our research, the most active members of the COB LED communities tended not to speak highly of Cree chips. It’s not so much that they don’t work, but you can buy other chips for cheaper which work at least as well, if not better.

One user we spoke to suggested Cree were 30%-50% more expensive than similar brands on the market, and after testing the equivalent Citizen and Bridgelux models they found Cree to be less light intensive.

Depending on the size of your grow room or grow tent, reflectors can be used to focus the light in the direction you’d like. COB LEDs have a shining angle of approximately 120° but the reflectors narrow this to around 90° which can make a big difference in larger growing areas.

A lot of the main LED manufacturers create tools so you can easily compare between their products to suit your needs. As several manufacturers do this, you can then compare between the brands, too.

Here’s Cree’s tool

Here’s Bridgelux’s tool

Here’s Citiled’s tool

This gives you the opportunity to see which COB LED will work best under the conditions you plan on using them. Depending on what your plants deem optimal.

Quantum Boards

Quantum boards are even newer than COB LEDs and were designed by the Horticulture Lighting Group who gave them their slick name.

The diodes are placed in parallel lines and work with high-powered constant current drivers. There are two types on the market called the QB304 and the QB288, the number references the amount of diodes in the quantum board.

The diodes are made by Samsung, the models are LM561C. These are really efficient with efficacy at around 200 lumens/watt. Forward voltage is ~2.7-2.8V and 65mA.

Are quantum boards better than COB LEDs? Well, they’re essentially the next stage in COB development. They work on the same principle but are in contact over a larger area, making them one really big COB.

With Quantum Boards you won’t have to worry about overheating as much, they don’t need active cooling on their heat sinks. Their light production is distributed more evenly over the area of around 1’. Thus, fewer hotspots but maximum illumination. Your plants will grow happier. COBs typically have an efficacy of approximately 150 lumens/watt, whereas quantum boards are reaching about 180 lumens/watt.

If you want to build quantum boards yourself, know it’s trickier and the cost is still relatively expensive. You could purchase several decent COBs for the same price which may well be a valuable consideration.

They’re still in their infancy but quantum boards look like a promising next step in lighting technology.

have you seen our other Articles on hydroponics?

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