May 07 2020
LED vs. HPS: Why Making the switch to LED is a smart move
Deciding on what growing lights to use in your indoor garden is a major decision, with trickle-down effects not only on your potential harvest but the entire operational setup. Today, there are two main types of indoor grow lights to choose from, high-pressure sodium lights (HPS) or light emitting diodes lights (LED). The ongoing debate between the two very different lighting options is fierce with experts weighing in on both sides. But recently, as LED lighting companies continue to make improvements to their products, the tide is moving in their favor.
Why is making the switch to LED making more sense for indoor growers than ever before? In recent years, the upfront costs for LED lights have dropped dramatically, technologies have improved to better harness the science of light, and producers recognize the energy-saving potential of LEDs.
Many indoor gardeners were wary of LED lighting options in the past because they had experienced older, outdated versions, released well before many of the current innovations were around. But today, even long-time growers are deciding to switch from HPS setups to more technologically advanced LED options; the pro-LED arguments are more and more convincing.
Considering the size of some indoor facilities in the ever-expanding indoor gardening market, electricity costs are easily one of the highest expenses. In a recent study, researchers present statistics showing lighting eats up on average 38 percent of total energy use. This makes it the largest part of a company’s energy costs.
While it is true LEDs have experienced a drop in price over the previous few years, it's also true they are still a considerable upfront cost when compared to traditional HPS systems. But, according to the study cited above, most LED fixtures will pay themselves off through energy savings alone within two to four years.
There are relatively few unbiased or well-conducted studies on the full cost-saving potential of making the switch to LED grow lights. After all, do you include the cost savings for reduced ventilation and humidity burdens? What about the reduced air conditioning burden? Also, there are significant differences between LED brands, how do you compare those? Some growers have tried to do the math, and estimate over the course of a year they save anywhere between 50 to 60 percent on their energy costs after switching to LEDs.
Some comparisons can be gleaned from non-agricultural uses; there is much more research comparing HPS to LED lighting in industrial operations for example. In a recent case, the city of Phoenix, Arizona began replacing their HPS street lights with LEDs. The city is projected to save over $2.5 million, through the replacement of 95,000 street lights in only ten years time. This takes into consideration the additional upfront costs of the LED fixtures. It’s highly likely that making the switch to LEDs for indoor gardening will see related cost-saving benefits.
The amount of heat emitted by lighting is one of the indicators of its efficiency. Based on the overall performance, around 80% of the energy emitted by HPS and CFLs comes out as heat, while LED grow lights release only 15% to 25% of their energy as heat. With LEDs spending most of their energy for producing light, it is easier to avoid too much heat which may be harmful to the crops.
If you’re planning a long-term growing operation, the lifespan of a particular grow light is as important as its efficiency and the upfront cost. Usually, HPS last about 10,000 hours on average, while CFL grow lights will run for around 8,000 hours. As a result, they need to be replaced with new ones every 2 years or less. LED grow lights, on the other hand, last much longer than the above options, as they can work up to 50,000 or even 100,000 hours. Therefore, you can use them for 5 or 10 years before they need replacement.
Grow Room Temperature
HPS bulbs can reach 750 degrees on the surface, and if not controlled properly with expensive equipment, can lead to a host of issues including stunted plants, wispy flowers, and rapid drying of medium, which would result in root mass loss, nutrient deficiency or toxicity, and even entire crop failure. LED grow lights run cool, so cool in fact that no additional temperature control equipment is needed besides the internal circulation fans. Lower light temperatures lead to a much more easily maintained grow environment in which your plants can thrive. Cooler temperatures also save on water and expensive nutrients that evaporate in high-temperature rooms. Cooler root zones create larger, healthier root balls, which will ultimately lead to larger yields. In addition, oil production on plants is unharmed by lower temperatures, whereas high temperatures from HPS lighting degrade oils, sometimes stripping them completely from the tops of fruits and flowers. Keeping the plant's natural flowering oils intact will lead to much better tasting and smelling fruits and flowers.
Improvements to Light Science
Another major reason why LED growing lights are starting to take over the market is that they have drastically improved in quality since the early days. The argument for HPS has always been that HPS emits a much higher intensity light than LEDs, and therefore growers argued, there was much more potential for yield.
While this point was true for the LEDs of old, there are drastic differences between the high-quality LEDs today and those from the past. Innovations in LED technology have focused not so much on intensity (although this has improved) but on the light spectrum required during each stage of a plant's growth cycle.
Historically HPS produced higher lumen output than most affordable LED models, but this is quickly changing. So too is our understanding of what types of light plants require through their growth cycle. High-pressure sodium lights emit on the orange, yellow, red light spectrum, and yet scientists have recently discovered plants require more blue, red, and UVA during the two most essential stages: the vegetative and flowering stages. This research has been incorporated into the newer models of LED lighting, which focus specifically on the light spectrum required for indoor gardening.
The pro-HPS arguments are quickly falling apart, as LED technology is evolving in smarter and smarter ways. Even beyond the brief arguments made here, there are further reasons why indoor growers are making the switch. Energy efficient lighting technology eliminates a significant burden on heat and dehumidifying systems, there are often government subsidies for implementing green tech, and LEDs are often one-piece fixtures making them much simpler technologies to install and manage. Experts predict LEDs will soon be shining on all the majority of indoor grow operations.