Advancements in horticultural lighting seem to be moving at the speed of light. OK, not actually at 186 million miles per second, but advances in efficiencies and spectrums are now seemingly daily occurrences. Even better is that all these advances are being coupled with decreasing prices.

As I review advancements in horticultural lighting, I am absolutely gobsmacked by the rate at which technology is improving. Plant-specific lighting continually evolves, capitalizing on the newest technological innovations and our increasing understanding of photobiology.

Considering the electric lightbulb was patented in 1879, and where we are today, it takes a fair amount of effort to keep up with this fast-paced, ever-changing technology. Well, I am here to make your lives easier and give you an overview of some of the latest innovations in horticultural lighting. The biggest lighting trends so far this year include:

  • The widespread acceptance of double-ended HID (high-intensity discharge) lighting.
  • The availability of 1,000-W digital, low-frequency ballasts with square-wave technology that are pushing the needle of efficiency and PAR output.
  • Ceramic metal halides that are producing high CRI light using less electricity.
  • The use of chip-on-board (COB) LEDs that are making LED lighting more functional and affordable for the masses.

Double-Ended HID Lamps

Metal halide lamps were first invented in 1912 by Charles P. Steinmetz, who was the first to use halide salts in a mercury vapor lamp. High pressure sodium lamps as we know them today were first introduced in 1964 by Louden, Schmidt and Homonnay, a group of scientists working for GE in Cleveland, Ohio.

Since their introduction, these two types of HID lamps have dominated the industry and became the standard in lighting for horticulture. Although the lamps have benefited from several innovations, none have made as great an impact as the introduction of double-ended (DE) HPS and MH lamps.

Double-ended HID lamps are capable of producing 1.7 µmol/watt compared to the original core and coil ballasts of the ’70s that produced 1.02 µmol/watt, or the more recently innovated high-frequency electronic ballasts of the ’90s/2000s, which produced 1.3 µmol/watt.

Double-ended lamps also boast decreased lamp degradation, where, at 10,000 hours (under ideal environmental conditions) of operation, their output is only reduced by four per cent compared to traditional, single-ended HPS lamps.

Single-ended lamps at 10,000 hours have lost roughly 25 per cent of their original output. Combine the increased efficiency and improved longevity od DE lamps, and then couple that with increased yields, and you have some of the best new lighting available.

Square-Wave Technology

Moving forward, it is going to be hip to be square—square wave that is. Square-wave technology takes DE lighting to a new level. Almost all modern electronic HID ballasts (those that fire single-ended or double-ended lamps) provide power to the lamp using a sine wave design operating at an ultra-high frequency of roughly 120,000 hertz.

Square-wave ballasts provide a more constant maximum voltage to the lamp for a longer period of time that produces more photons of light for your plants. Additionally, the lower frequency will not cause any issues related to RF interference. The square wave design will improve the performance of any brand of lamp DE lamp.

These lighting systems will produce an even, steady arc stream inside the arc tube because of their ability to provide a consistent power supply. This produces an even, consistent spectral output.

Lesser ballasts produce acoustic resonance inside the lamp (the waving and swirling of the arc stream), which will cause color shift, frequent lamp restarts and eventually premature lamp failure. So come join the sock hop and get square!

CMH Lighting Systems

Also capitalizing on low-frequency, square-wave technology are the ceramic metal halide (CMH) lighting systems. Incorporating low-frequency, square-wave digital ballasts and a more optimal blend of gasses in their ceramic arc tubes, these lights produce a full-spectrum white light with a color-rendering index (CRI) ranging between 90-92 (sunlight has a CRI of 100 and an HPS lamp is about a 25).

CMH lamps are generally 315 watts, although some companies are offering double-lamp units for a total of 630 watts. The lamps are available in a full-spectrum, 3,100 K version and also in a high-blue spectrum, 4,200 K version that is better for vegetative plants. The lamps also tout a two-year, 20,000-hour replacement recommendation. CMHs produce more light per watt than single-ended HID lamps.

Therefore, when used as a replacement for older single-ended HID light systems, they can lower your electrical bill and the overall heat-load in your garden while still maintaining the same light intensity at the plant canopy. The low-frequency operation of CMHs also removes the potential for radio-frequency (RF) interference from your equipment as an added bonus.


As few as 10 years ago, LED grow lights were nothing more than Lite-Brite toys from the late ’60s. They produced a purple-colored light from a mixture of red and blue LEDs. Unfortunately, the early LEDs were terribly ineffective at growing plants. Moving away from the red and blue diodes to full-spectrum white light, and combining high intensity with energy efficiency, the latest COB (chip on board) grow lights on the market are not only easy on the eyes but have made huge advances in their ability to grow plants.

COB LEDs are a relatively new way of packaging multiple light emitting diodes onto a single module. By grouping them together they are easier to integrate into an effective grow light—50 individual LEDs can be replaced by a single COB LED. Grouping the LEDs together also gives them an increased surface-cooling area and advantageous thermal resistance.

COB LED grow lights underdrive the nominal power of each COB to maximize light output efficiency. Running them at roughly half the rated power increases their output efficiency and minimizes their heat output.

HPS lights have a radiant efficiency (sometimes called wall-plug efficiency) of 30 per cent, meaning 70 per cent of the electricity used by the system is converted into heat. The new COB LEDs can achieve efficiencies of 40-50 per cent.

With all these improvements being made to new lighting technology, now might be the time for you to upgrade your outdated, inefficient lights from yesteryear to some of this new technology.

Plant lighting has never been so inexpensive, so don’t buy a cheap relic from the past! For more information on these new lighting trends, ask your hydro shop reps, who have made it their mission to stay up to speed on today’s lighting options.