High intensity discharge (HID) lamps are the standard artificial lighting source for many indoor cannabis gardeners. Although LEDs and induction lighting technologies are also being utilized by cannabis cultivators, HID lighting systems still reign supreme in terms of providing an intense light source within an enclosed environment. Due to the fact that state laws regulate both recreational and medical marijuana grow operations by the number of plants a gardener can possess, many cannabis gardeners choose to grow the largest plants possible. Simply put, they do this to maximize the yield from their limited plant numbers.
Growers who cultivate monster plants need an artificial light source with an intensity strong enough to penetrate the plant’s canopy and to deliver a spectrum suitable for plant growth. This is why the lighting solution for so many growers is HID lighting systems. HID lighting systems consist of two major components: the ballast and the lamp. Most HID lighting systems also utilize a reflector of some sort to direct the majority of the light energy toward the plants. Metal halide (MH) and high pressure sodium (HPS) lamps are the old standard in HID lighting, while ceramic metal halide (CMH) and double-ended high pressure sodium (DE-HPS) are the HID lighting choices of today’s indoor cannabis growers.
All HID lighting systems require a ballast for operation. The ballast is the component that connects directly to the power source and acts as a regulator for the electric current. Essentially, the ballast makes sure the lamp is not overloaded or underpowered when it is illuminated. HID lighting systems require an initial burst of current to strike the lamp (light the bulb) and this is regulated by the ballast. After a lamp is lit, the ballast continues to regulate the current so that it does not overload the lamp.
HID lamps most commonly found in horticulture consist of metal halide, high pressure sodium, ceramic metal halides, and double-ended high pressure sodium. Most cannabis horticulturists choose lamps that are specifically made for horticulture. Horticultural specific lamps are specially designed to maximize the amount of photosynthetically active radiation (PAR) that is emitted. In other words, these lamps aim to produce the highest amount of usable light energy for plants. Lamp manufacturers are continuously testing methods of construction and experimenting with various internal components to heighten PAR output.
Double-ended bulbs differ from standard HIDs in that they have connection points at both ends of the bulb instead of a single mogul base. DE bulbs are made for high-frequency digital ballasts and require special reflectors/sockets for operation. The manufacturers of double-ended bulbs advertise higher light outputs because the unique lamp design removes the need for an internal frame wire. This eliminates the shadow otherwise created by the frame wire. Cannabis growers have jumped on board with double-ended lighting systems because they provide the most intense lighting in the most efficient manner possible. In other words, DE lighting systems give gardeners the ability to grow really big plants indoors. All in all, the HID lighting system of choice for many cannabis growers is the double-ended high pressure sodium.
The biggest advantage of DE technology is its heightened efficiency. This heightened efficiency is extremely valuable to an indoor cannabis horticulturist. DE technology offers a way for marijuana growers to increase the productivity of their indoor gardens without using more electricity. It may sound too good to be true, but even professional growers are consistently being impressed with the results they are obtaining with DE technology lighting systems.
In addition to electrical efficiency, another huge advantage of DE technology is increased bulb longevity. The lamp longevity of DE technology is attributed to the technology’s higher operating frequency. The electricity’s ability to flow through the bulb, instead of into the bulb at one end, is what allows DE bulbs to operate at a higher frequency. The higher frequency combined with the fact that the lamp is fired from both ends (which is more effective at converting the gases within the bulb into useable light) equates to a slower break down of PAR.
Lamp longevity is a big consideration for cannabis growers, especially those with large grow operations where replacing bulbs is a significant expense. DE lamp manufacturers claim 90%+ lumen output at 10,000 hours. A manufacturer of a typical single-ended HPS lamp claims 80-90% lumen output at 4,000 hours. For a cannabis grower, this means less bulb changes per year and a higher return on investment. Generally speaking, marijuana growers should be able to use DE lamps for about twice as long as a standard HID lamp.
As mentioned previously, DE lamps are fired from both ends. A lamp burned at both ends will automatically burn the gases within the bulb more evenly which results in an increased output and better overall spectral output. Basically, the gases within a double-ended bulb are not going to waste, but, instead, are being more efficiently burned. All in all, this equates to a higher PAR value being emitted from a DE lamp than a single-sided HID lamp. For cannabis growers, this means more electricity is being converted into usable light energy for their plants. Double-ended lamps are secured at both ends so there is never any chance that the lamp will sag and create an uneven footprint. Simply put, if the reflector of a DE lighting system is hung level, the footprint will be even.
In addition to double-ended high pressure sodiums, another HID technology utilized by savvy cannabis cultivators is ceramic metal halides (CMH). Ceramic metal halide lamps contain an arc tube (much like a HPS lamp), but also use a mixture of halides and gases in the arc tube (much like a MH lamp). In other words, a ceramic metal halide is almost like a hybrid between a MH and a HPS lamp. To produce a comparable light output, CMHs consume less power than HPS or MH HID technologies. This heightened efficiency is a big advantage for cannabis growers who are always on the search for the maximum light output at the lowest electricity usage. CMHs are also a low heat signature lighting technology. Less heat emitted not only equates to a more efficient light output, it also decreases the need for cooling equipment, which, in turn, increases an indoor cannabis grower’s overall return on investment.
The heightened efficiency and lower operating temperature have many cannabis enthusiasts excited about CMHs. However, it is the spectral output of this technology that is most impressive. Ceramic metal halides have a full spectrum output and a color rendition index (CRI) rating around 90. Light from the sun has a CRI of 100, so a ceramic metal halide is capable of delivering an intense spectrum very close to that of the sun. Ceramic metal halide lamps also produce a good amount of UV rays. UV light is advantageous for cannabis growers because it promotes additional essential oil production. Put another way, using a CMH lamp will increase the production of cannabinoids and terpenes found in a cannabis plant’s essential oils. Like DE-HPS lamps, ceramic metal halides have a longer life span than the standard metal halide or high pressure sodium lamps. Ceramic metal halide bulbs have a rated life span of 20,000 hours, whereas many horticultural specific HPS lamps have a rated life span of 10,000 hours.
High intensity discharge lighting systems have been at the forefront of indoor cannabis production since the beginning of indoor horticulture. Lamp manufacturers who specialize in horticultural specific lamps are continually upgrading their lamps to produce more PAR per watt of energy consumed. As long as the laws surrounding cannabis cultivation continue to regulate the number of plants a grower can possess, horticulturists will rely on lighting technologies capable of growing large marijuana plants indoors. Currently, HID lighting systems are the best choice for growing gigantic plants indoors. Of all the different technologies within the HID realm, cannabis growers are flocking to double-ended high pressure sodiums and ceramic metal halides.
These two particular technologies maximize the amount of usable light energy compared with the electricity they consume. The high frequency ballasts combined with a bulb that electricity flows through makes double-ended HID lighting stand out among other artificial horticultural lighting sources. However, the longevity and incredible color rendition index of ceramic metal halide along with its ability to provide higher amounts of UV light for increased essential oil production have many cannabis growers flocking to that technology. Whether it be a double-ended high pressure sodium, a ceramic metal halide, or both, marijuana growers who utilize the latest in HID lighting technologies will be able to grow the largest plants in the most efficient and effective manner possible.
Eric Hopper is a Professional Marijuana Grower Senior Editor.