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Are LED or HPS Lights Better for Growing Cannabis?

July 22, 2020 February 4th, 2022 No Comments

What are LEDs?

Light-emitting diodes (LEDs) are a type of light source that uses solid-state semiconductor chips to produce light when an electric current flows through them. This allows them to produce more photons (light) while using less electricity than older HID technologies, such as high-pressure sodium (HPS) lights or ceramic metal-halide (CMH) lights. LED light sources have been found in commercial products for nearly half a century, but they have only recently begun to see use in indoor horticulture.

Originally, LEDs were not capable of producing the intensity of light in the wavelengths required for indoor grow operations. The first generation of cannabis LED grow lights were lacking in power and produced only red-blue light, which led to the nickname “Smurf Lights.” These were not capable of matching the yields produced using traditional HPS light sources and led many cultivators to write of LED technology for indoor horticulture. In recent years, advancements in the color and intensity of light created by LEDs have allowed for the creation of powerful full-spectrum LED grow lighting that can match or exceed the yields of traditional lights. This has led to the rapid adoption of LED technology for indoor grow lights as cultivators recognized their unique advantages over traditional lighting technologies.

Advantages of LED Grow Lights

Use Less Energy

LEDs use far less energy to produce the same amount of light when compared to HPS or CMH. This can be measured using efficacy, which takes the amount of light produced by a grow light (µmol/s) and compares it to the amount of energy used (Joules/s). A Double-ended HPS fixture like the one made by Eye Hortilux can produce 1950 µmol/s while using 1000W of power giving, it an efficacy of 1.95 µmol/J. The VOLT Grow® Full-Cycle Grow Light can produce 2000 µmol/s while using only 720W giving it an efficacy of 2.7 µmol/J. That makes the VOLT Grow® FL-1 light nearly 30 percent more efficient than the 1000W DE HPS fixture. For cultivators who have limited access the electricity, this can mean being able to have more lights at your facility without exceeding your building’s energy limits or compromising light intensity.

Opportunity for Rebates

A unique benefit for cultivators purchasing cannabis grow lights using LED technology is the availability of rebates from utility companies. With the recent boom in indoor cultivation, utility companies are seeing unprecedented demand for electricity, which puts immense strain on the grid. In order to combat that strain and to promote environmentally-friendly growing techniques, electric companies are offering rebates to cultivators who purchase approved high-efficiency LED grow lights instead of the more power-hungry HID style lights. Depending on your local guidelines you can have anywhere from 20 percent to 90 percent of the total cost of the LED grow lights you purchase refunded by your local utility company. Anyone can take advantage of these rebates, regardless of whether or not they have a cultivation license or if the crop they are cultivating has been legalized in that state. The only goal of the rebates being offered by the electric companies is to curb the demand being put on their grid. The size of the rebate is dependent on your local utility companies’ guidelines and the configuration of your grow. Most only offer rebates for grow lights that have been approved by the DesignLights Consortium (DLC) as being highly efficient. Rebates must be applied for and approved prior to purchasing your indoor grow lighting and compensation is normally only given months after the approved order is made. VOLT Grow® has a team that can handle all of the paperwork and applications needed to get the maximum rebate for your grow light purchase.

Produces Less Heat

Due to the energy efficiency of LEDs, grow lights using LEDs create much less heat compared to traditional light sources. HPS and CMH fixtures produce lots of heat when operating which, besides making them less efficient, creates a number of issues and limitations for indoor growers. In many places, particularly warmer climates, that excess heat needs to be removed from the grow room to maintain an optimal temperature for your grow environment. This means installing and running expensive HVAC (air conditioning) systems in your grow room. These systems use large amounts of energy to lower the temperature of your grow environment, which increases the operating cost of your grow. Since LED grow lights produce much less heat, those HVAC systems will not have to work as hard to maintain an optimal temperature for your grow room thus lowering your cost.

Can Hang Closer to Canopy

A secondary benefit of LED grow lights producing less heat is that they can be placed closer to the canopy of your plants. HPS/CMH grow lights can burn plants if placed too close to the canopy due to a large amount of heat they produce. This means you need to leave more space between them and your canopy. LED grow lights can be placed as little as a foot above the canopy which offers a number of benefits. First, it allows you to grow vertically on racks. Multi-level grow operations enable cultivators to grow more plants in less space than would traditionally be needed. In regions where space is limited or real estate is expensive, multi-level grows can increase a cultivator’s output while reducing their expenses. Additionally, placing your grow lights closer to the canopy increases the amount of light that reaches your plants. Light is absorbed by particles in the air. So, the higher your fixture is above your canopy, the less light will end up reaching your plant. Light spillage is also an issue in some grow set-ups. Lights hung higher above the canopy spread their light over a larger area. This can lead to light being wasted as it spreads out beyond the canopy and doesn’t hit any plants. Hanging your fixtures closer to the canopy reduces this effect and focuses light on the desired areas.

Full-Spectrum Light Output

The wavelength or spectrum of light produced by LED grow lights have been one of the most rapid areas of advancement. Plants in nature receive a wide range of wavelengths (colors) of light from the sun. Different wavelengths of light have different effects on a plant’s growth. The combination of wavelengths being produced by a light source is referred to as the light spectrum. Initially, LED grow lights were only capable of producing very specific wavelengths of light, primarily red and blue. This put them at a disadvantage to HID light sources with fixed spectrums that were closer to what plants needed. With advancements in LED technology, we are now capable of making full spectrum grow lights that are perfectly tuned for each stage of plant growth. Unlike the single fixed spectrum produced by HID fixtures, LEDs come in a variety of colors allowing them to be mixed and matched to create a spectrum of light optimized for plant growth. This results in higher yields as light is being delivered to the plant in a form that is easier for them to use in photosynthesis. For example, during the vegetative stage of growth, you may want more blue light which has been shown to make plants stockier, while additional red light may be desirable during flowering to promote growth (stretch) and flowering. Tailoring the spectrum of your light is an option only offered by LEDs as HIDs are only capable of producing one spectrum of light.

Longer Life Span

Another major advantage of LED chip technology is its longevity. Our grow lights can last 50,000 hours before their light output is significantly reduced. This means that on average grow lights using LEDs can have close to 10 years of normal use (12hrs On – 12hrs Off) before they need to be replaced. For comparison, the lamps used in HPS grow lights are typically swapped after only 12 months of normal use and can cost over $100 to replace. Even with their lower initial cost, in just a few years HPS grow lights can become more expensive than LED lights once the cost of replacement lamps is factored in. When you also take into account the additional savings LEDs provide by being more energy-efficient, less demanding on cooling systems, and eligible for rebates, LEDs are the more cost-effective lighting solution.

How to Adapt Your Cultivation for LED Grow Lights?

With traditional HPS and CMH grow lights dominating the market for the last couple of decades, many growers are having to learn how to adapt their grow operations to suit cannabis LED grow lights. Countless variables must be taken into account when optimizing a grow room and changing the type of grow lights being used impacts many of them. When retrofitting a grow room that used HPS or CMH grow lights, you may need to do more than just swap your grow light fixtures with new LED lights.

As previously mentioned, LEDs produce far less heat than their HID counterparts. This means you may need to tweak your HVAC or heating systems to account for having less heat produced in your grow room. In warmer climates, this means not having to pump as much heat out of your cultivation room with HVAC systems. In cold climates, you may need to bring in more heat using gas or electric heaters in order to keep your room at an optimal temperature. It’s worth noting that even in colder climates it is still better to use more efficient LED grow lights with supplemental heaters than it is to rely on inefficient HPS/CMH grow lights to simultaneously provide both light and heat. HPS/CMH grow lights produce heat less efficiently than a dedicated heater and must be turned on in order to do so. This means that during off cycles, you may still need to rely on dedicated heaters to keep your room warm. Additionally, during warmer seasons the excess heat produced by HID fixtures may become negative and require HVAC to remove the now unwanted heat.

Additionally, the humidity will be affected when switching to LED grow lights. When the heat from light hits a plant, the water inside of and around the plant is evaporated into the air. This raises the humidity in your grow room. When switching to LED grow lighting, cultivators may not need to use as many dehumidifiers as they had in previous HID grow rooms.

The way your grow light is mounted may also need modification when switching from HPS/CMH to LED. Because LED grow lights can be placed closer to the canopy, many growers will rig their lights so they can be raised and lowered. Because the grow lights can be moved as the plants grow, they can stay as close as possible to the top of the canopy. Keeping the lights close to the canopy increases the amount of light the plants absorb and use for photosynthesis

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