Just 10 years ago, LEDs had yet to find a place in the indoor gardening market. The high price tag, teamed with disappointing results, made most serious gardeners avoid LEDs like the plague. Today, things are much different. Horticultural LEDs have found a solid place in the market and continue to increase in popularity. Much of this has to do with the numerous benefits offered by LED technology.

Cooler operating temperatures, longevity and the ability to customize spectral outputs are some of the benefits of using LED grow lights. And there are now many companies offering these lights at an affordable price. The more-affordable price, combined with all of the other benefits of growing with LEDs, has both novice and professional growers turning to LEDs as their primary light source.

Unfortunately, it is not always easy to distinguish a good LED lighting system from a bad one. Many variables must be considered when determining the effectiveness of an LED grow light. If you’re hoping to find the best and brightest LED on the market, you will need to take a close look at the components that most affect the lighting system’s efficiency.

For example, an HID lighting system has three components that affect the lighting system’s overall performance: the bulb, the ballast and the reflector. An LED lighting system has four components that significantly affect the system’s overall performance: the driver, the lens, the heat-sink and the LED itself. Let’s look at each component in some detail.

The Driver of an LED Lighting System

An LED driver is an electrical device that regulates the amount of electricity delivered to the light or string of lights, similar to an HID system’s ballast. LED drivers respond to the changing needs of the grow lights by providing a constant quantity of power to the LED as the electronic properties change with temperature.

The driver also converts the AC from the wall outlet to DC for the diodes. LEDs are low-wattage light sources that require a constant DC voltage to operate optimally. Each LED has a manufacturer’s recommendation when it comes to voltage or current. If the current exceeds the manufacturer’s recommendation, the LEDs may become brighter but the light output will degrade at a faster rate due to the increased temperature, so it is important that the LED driver is sized according to the manufacturer’s recommendations.

This brings up one of the most confusing aspects of LED lighting: the wattage draw. Many companies advertise horticultural LEDs by both the lighting system’s theoretical wattage draw and its actual wattage draw. The theoretical wattage draw refers to the total amount of wattage draw possible for the unit.

For example, a system with 20 diodes capable of 5 W each would have a theoretical wattage draw of 100 W. However, if the drivers within the system allow each of the 20 diodes to consume only 3 W, the actual wattage draw of the unit is 60 W. Why would anyone want to use a driver that would only supply 3 W to a 5-W diode? The answer is longevity. By operating a 5-W LED at only 3 W, the longevity of the diode increases greatly.

Essentially, the heat from the additional wattage would make the LED lose intensity more quickly. Although there are good reasons for the existence of the theoretical draw on LED lighting systems, it can be confusing for consumers. When comparing LED lighting systems, closely examine the lighting system’s actual wattage draw versus the theoretical wattage.

The Lenses

The lenses for horticultural LED lighting systems can be split into two categories: primary and secondary lenses.

Primary Lenses

The light emitted from an LED is the result of the current passing through the silicon in the diode. Primary lenses are placed directly on the light-emitting portion of the diode to increase the amount of light that emits from the silicon. Most LED systems use primary lenses. It is more efficient to do so and does not increase the cost of the unit.

Secondary Lenses

Secondary lenses are placed beneath the primary lens to help focus the light into a wider or narrower beam. Secondary lenses don’t increase the amount of light being emitted; they help direct the light to better suit a particular application. Many LED manufacturers use secondary lenses as a way to focus the light into a more intense beam. The problem with this is that as the light is focused and the intensity increases to one area, light diffusion is lost and the total coverage area is decreased.

The Heat-sink

A heat-sink is a passive heat exchanger that transfers heat from an electrical device to a coolant. For horticultural LEDs, the heat-sink transfers heat from the LED or string of LEDs to the air, which acts as the coolant. Most heat-sinks look like big, thick, metal combs and are usually placed near the unit’s cooling fan.

The teeth of the comb allow the heat produced by the electrical current to be transferred to the air. When shopping around for a lighting system, it is important to examine both the heat-sink and cooling fan.

Larger heat-sinks combined with a cooling fan are nice for indoor gardens because the ambient temperature of an indoor garden can run higher than normal living quarter conditions. If the system is not effectively cooled by its heat-sink and fan, the unit will operate less efficiently and degrade at a faster rate.


Just as not all HID light bulbs perform the same for horticultural purposes, there can be a lot of variety in the diode, or LED itself, in a lighting system. The spectrum emitted by the diode is crucial to the effectiveness of the lighting system. Particular wavelengths of light are more easily absorbed by plants during photosynthesis and are used more frequently by plants than other spectrums.

In fact, some wavelengths of light are hardly used at all by plants. Lighting systems that produce the most usable ratio of wavelengths will be more efficient than those that do not. This is the main reason why LEDs are so exciting for the indoor gardening industry. The ability to customize LED lighting systems means not only more efficient lighting systems, but also the ability to experiment with the way plants respond to particular ratios of light wavelengths. Because of their customizability, LEDs will play a huge role in the evolution of indoor gardening.

Aside from the actual color of light the diode produces, the quality of the diode should also be taken into consideration. Think of each diode as its own electrical device. The materials used and the manner in which it was constructed are significant to the diode’s light output and longevity. Just about every LED manufacturer uses a tier system when grading their LEDs. It is always a good idea to ask manufacturers a lot of questions when comparing LED lighting fixtures, including which tier their diodes come from.

Finding the Right Light for Growing Plants

Not all horticultural LEDs are equal, and when looking at the specs of a system, you should pay close attention to the components used in manufacturing the final product. The driver, the lenses used, the heat-sink and the LEDs themselves all play significant roles in the lighting system’s effectiveness for growing plants.

By closely examining the amount of PAR (photosynthetically active radiation) produced by a light compared to the light’s actual wattage draw, you can make a fairly accurate prediction as to how efficient the system will be. Due to the number of variables that affect an LED’s performance, it can be difficult to find the right LED for your garden.

However, if close attention is paid to the quality of the components used and the light’s PAR output versus the actual wattage draw, you can find the right system to meet your unique needs.