LED grow lights are more expensive than HPS, but many of the larger professional growers won’t grow with anything else. Self-sufficient home growers are migrating to LED faster than ever before. But the cost of a new LED means it is probably the most expensive grow room upgrade you will ever make. So, is it really worth the money? Let’s start off with a few simple technical basics.
LED ‘chips’ and COBs.
Many LED grow lights use traditional LED ‘chips’, usually these consume around 3W each, sometimes a little more, sometimes less. The top manufacturers include Osram, Philips, Cree etc. Often a grow light will have dozens of these LED chips, they are bright and available in a range of wavelengths. COBs are higher power, each one can consume 50W or more and can be thought of as similar to a large LED light source with a higher power draw.
Cooling. Active vs. Passive cooling.
The best LED growlight manufacturers keep the LED chips and COB’s as cool as they can. This enables the best LED grow lights to retain around 80-90% of their light output even after many years of use. Passive cooling allows heat to radiate silently away from a metal heat sink. Active cooling often uses a fan to blow air over the LED metal heat sink. This may make a low humming noise, for bedroom growers that could be an issue. Active cooling may come with slight fan noise, but it’s a good way of helping keep the LED extra cool. In reality both methods work well. Passive cooling is preferred by those that favor absolute silence and inherent design simplicity.
Purple vs. white spectrum. They both work fine.
White spectrum LEDs are the most user friendly to grow with. The spectrum usually appears as warm white, similar to a summer evening glow. It’s an easy light in which to check the leaves for nutrient deficiencies and overall plant health. Many first time LED buyers choose a good brand with a white light output and love the investment. And results are great too, in the many checks by our growers we see some excellent results from the best of the white-light spectrum LED grow lights.
Blue/Red LED lights are preferred by some growers. The blue and red wavelengths of light produced by the LEDs are deliberately selected for absorption by the chlorophyll. These lights may have around 80% red LEDs (around 640nm) and 20% blue LEDs (around 440nm). These correspond to the absorption points of chlorophyll ‘’a’ & ‘b’ molecules. The purple light is more difficult to work in than white light but some growers love it and feel the productivity is hard to beat.
Adjustable spectrum and power.
Depending on your budget, you can get LED grow lights which allow you to control both power and spectrum. California Lightworks, Ursa, Fluence and others allow you to dim the power for small plants. Companies such as California Lightworks and Grow Spec allow you to adjust the ratio of the light spectrum. This allows you to specify a more blue dominant spectrum during early growth and a red dominant spectrum during bloom. Some of the grow lights allow you to program sunrise and sunset modes which are thought to allow the plant a less stressful transition between night and day. Many of the large professional growers demand the ability to adjust power and spectrum. Serious hobby growers also appreciate the ability to control power and light spectrum.
Adjustable LED spectrum. Quality counts.
Adjustable spectrum opens up a whole new world of possibilities. If your sativa is stretching too much simply reduce red light content and increase the amount of blue. This allows you to keep your favorite sativa genetics short and compact enough for your indoor tent. And if you have an excessively compact indica, then try reducing blue light content and increasing red light to increase internodal distance. This will allow you to stretch your indica to a larger size and aim for a larger yield. Many growers now use the ‘blue light treatment’ at the end of bloom to increase terpenes and potency. This is done by turning off the red spectrum at the end of bloom for 2-3 days and just providing blue light to the plants.
Daisy chaining the LED grow lights.
Larger professional growers often need to daisy chain several (or even hundreds) of grow lights into a circuit which illuminates their entire grow room. Not all LED lights can be daisy chained and remotely controlled, but for some growers it is essential to select an LED brand which allows this.
Traditional design. Panel LED grow light e.g. California Lightworks, Ursa, GN, Oreon.
In the LED ‘panel’ design, all the LED chips are packed together in a panel or ‘point light source’. The power draw can be several hundred watts. These lights have the advantage that they can be hung at the top of the grow room and will create a light spread which will fill the grow canopy. The high intensity output means these lights have to be hung high up to prevent LED light burn, these are far too powerful to position 20cm above the crop canopy. Having the light hung up high means you can get in and work on your plants with the grow light way above your head and out of the way. There may be a drop off in light intensity towards the corners of the grow room, but many growers simply live with that. Many growers (e.g. licensed producers) use these types of lights in greenhouses, to supplement natural sunlight.
Bar-style design. e.g. Fluence, SANlight
The other main LED grow light design is where the LED lights are positioned along multiple bars which are then placed close to the plants, often around 20cm above the canopy. This prevents the intensity reduction in tent corners – which is seen with lights which are hung high above the canopy. The advantage of the ‘bar-style’ design is uniform light spread across the canopy. The downside of bar-style LED grow lights is that you can’t get in as easily to work with your plants, inspect and feed them. And you will need to try to keep a flat and even canopy or it can get complicated. In our own test grows and customer grows we can say that the results from the Bar-style designs produce equally good results as LED grow lights which use a light panel. Much depends on your style of grow. If you are growing hundreds of identical clones in a multi-level professional grow operation then a bar-style design is probably your best choice.
LED. And the main reason to upgrade is ?
For some people the main reason to upgrade to LED is to reduce grow room heat levels. A well built LED grow light produces much less heat than HPS. For some growers in hot climates, LED is the only way to grow during summer. Other growers like the fact that LED has none of the regular bulb replacements required by HPS, LED is maintenance free. Other growers, especially commercial growers that are required to keep energy usage below pre-set limits, like the fact that LED is inherently more efficient and uses less energy. But the main reason that most people switch to LED, and stay with LED, is due to the increased potency, terpenes and cannabinoid content in the harvest. Better quality cannabis with higher cannabinoid content commands a higher price in the legal markets as well as the illegal ones. In the legal US states, a dispensary would expect to pay a grower a significant price premium to get cannabis with 25% THC compared to cannabis with 15% THC.
LED, improved spectrum, improved plant growth.
LED delivers a much healthier light spectrum to the cannabis plant compared to HPS, without the heat stress. Terpene production is also better under LED, healthier plants give better harvests with superior aroma and taste. YouTube has plenty of good videos from large legal growers who are convinced that LED is able to take quality levels up a level beyond HPS. For home growers LED is a chance to enjoy stronger and more pleasurable harvests, as well as better quality crops during the hotter summer months.
LED. Initial outlay costs recovered in time.
For many people, the initial cost of investment deters their LED purchase. But, depending on the number of grows you make each year, most LED grow lights pay for themselves over a few years thanks to lower electricity costs and the savings made by not replacing the HPS bulbs. Of course, there is a quality increase as well which for some growers has a direct financial benefit on the crop value. The best advice we can offer is to avoid the lower quality LED grow lights which use cheaper, less powerful LEDs. Low cost LED modules are less reliable and use cheaper LED chips with less ability to penetrate light through the canopy. LED By Passion grow-tests all their LED brands on full cycle grow tests over 1-2 years and deals only with professional LED manufacturers. All the fully tested LED grow lights have warranties up to 5 years
By Tony, LED By Passion. (LED By Passion is a Dutch Passion company)
Originally published in Weed World Magazine issue 138