There is no perfect grow light…period. Heck, even the “big bulb in the sky” has its limitations—clouds happen. Every grow light has its strengths and weaknesses and this holds true for LED grow lights. Here’s a quick run-down on the pros and cons of LED grow lights.
What’s are the PROs for Using LED Grow Lights?
The No. 1 reason gardeners consider LED grow lights is the promise of a major reduction in electricity used. The latest LED grow lights typically provide a 40 to 50% reduction in lighting Watts consumed to illuminate an area when compared to other garden lighting sources.
By definition, one Watt of electricity produces 3.41 Btu of heat when consumed by any light-emitting source. LED, high-pressure sodium, metal-halide, florescent, induction and plasma lights all abide by this principle.
The basic reason LED lights produce less heat is less Watts are being consumed. Also, LEDs do not instantly convert more than half of the watts consumed into infrared heat, as their HPS/MH counterparts do.
Less Air Conditioning
Air conditioners might not be needed or can be run considerably less since there is less heat, saving growers money both in the operating costs of the air conditioner and maybe even the cost of buying the unit in the first place.
Using smaller exhaust and intake fans produce further savings. Smaller fans use less electricity and need smaller filters. Smaller filters cost less than larger ones. Many gardeners are forced to shut down for the summer due to external heat issues.
With lower heat output, LED-based gardens may be able to continue through the summer, keeping a garden’s revenue stream going year round.
LED grow lights are simple to install: just hang them up and plug them in. Hanging a bulky HPS/MH reflector, mounting a ballast somewhere nearby and installing a lamp is considerably more difficult than putting up an LED grow light. Additionally, you don’t need to remove the waste heat generated from the ballast when growing with LEDs.
No Lamp Changes
LED emitters typically have a 50,000-hour useful life. Once hung up, an LED grow light can be operated for more than 11 years on a 12/12 schedule with zero maintenance. During this entire period there are no lamp changes, which means no lamps to buy, drop, be burned by or dispose of as toxic waste. LEDs are the ultimate hang-and-forget lighting technology.
Even More Savings
Reflective wall coverings are popular in HPS/MH gardens—since HPS/MH lamps emit photons in every direction, many different types of wall coverings have been created to reduce hot spots and reflect all that light bouncing around back into the garden. These wall coverings are unnecessary in the LED gardens due to the highly directional design of LED grow lights.
Because HPS/MH gardens produce so much wasted heat, they often feature secondary fans that turn on at one temperature and off at another based on temperature readings from an on-board or separate controller.
Due to the lessened thermal load of LEDs, it might be possible to skip secondary fans. Also not needed are fans to air-cool lighting reflectors.
Reducing the number of ventilation fans not only saves the cost of the fans and controllers, but also the electricity to run them. In addition, the garden will be much quieter and require less space.
Because LED grow lights are considerably thinner and can be hung closer to the garden’s canopy, it may be possible to double-stack your garden. Assuming you have enough ceiling height—generally a minimum of 10 ft.—you might be able to double your growing space. Some major pharmaceutical companies are using LEDs in large, indoor, vertical farms that consist of 10 or more levels of stacked gardens.
What Are the CONs for Using LED Grow Lights?
No doubt about it, the initial cost of an LED grow light is considerably more than an HPS or MH grow light. All the return on investment calculations in the world can’t change the fact that you have to put down a bunch of money to get started. With LEDs, you pay more up front so you can pay less later in electricity and lamp replacements.
Any change you make to your garden, however small, can cause the need for other changes. Since light is the most critical item in the garden, changing it will definitely lead to other changes, such as the number and size of plants the garden can support, pruning techniques, nutrient strength, light/dark period temperatures and humidity.
Unfortunately, these changes are garden-specific; there is no table that says, “If you did this under HPS/MH, do this under LED.” The best advice when starting out with LED grow lights is to think like you’re a novice grower again, even if you have lots of indoor gardening experience. Go slow, watch your garden closely, think things through and don’t be afraid to experiment.
Wonky on the Eyes
LED grow lights typically produce a purplish color that can mask all kinds of indoor garden problems. Pest prevention is considerably more challenging under LEDs because the color of the light hides pest damage.
Once the damage is bad enough to be visible under LEDs, it’s often late into the infestation, when the most damage has already occurred. Invaders are more easily eradicated during the onset of the attack rather than later when they become more visible.
Just like pest damage, nutritional problems have a way of hiding under LEDs until it’s almost too late. Depending on the specific wavelengths in the LED grow light, the plants themselves can look dark—almost black in some cases. Your plants might look the same whether they are a lush green or almost completely yellowed and underfed.
Both problems can be solved with the same solution: turn off the LEDs and use “white” light to inspect the garden. Mount a regular compact fluorescent light somewhere in the garden or inspect it thoroughly with a 2-ft. fluorescent light bar. Take a really good look, not just a quick pass. This is your opportunity to head off problems before they begin. Do this at least once a week.
A quality LED grow light will be heavy because it includes an appropriately sized heat sink. LEDs need about 10 sq. in. of heat sink per watt of LED. Looking at the wattage of some of today’s high-powered LED grow lights, one can see the need for a large heat sink, which makes the lights fairly heavy.
Be sure your ceiling is strong enough to support the weight of the lights or reinforce it appropriately. A bit of framing work now can save a big headache later.
Growing Against the Grain
LED grow lights are still in their infancy stage. As is the case with adopting any early technology, you may find yourself going it alone. You can walk into any indoor gardening center and discuss a result or get a question answered about HPS/MH grow lights. Try going into your local store and asking LED-specific questions.
Most likely they cannot help you out of their personal experience, and at best will repeat some rumors they have heard about LEDs. They may even try to talk you out of using LEDs or swear that LEDs don’t work. By now, we have HPS/MH gardening pretty much down to a science, but collectively we don’t know much yet about how LED grow lights and plants interact.
You may find some indoor gardeners who claim to be experts are simply not ready to accept any new garden light, LED or otherwise. If you grow under LEDs, you will catch grief from these growers. This is typical when trying new things and growing against the grain. Don’t let them bully you: stay your course, tend your garden carefully and your results should speak for themselves.
Want more indoor gardening lighting advice? View the rest of Maximum Yield's LED lighting articles.