Benefits Of Using LED Supplemental Lights In Greenhouses 2021

9 min readFeb 10, 2021

Why Use Supplemental Lighting In A Greenhouse?

Greenhouse growing is highly automated, and in greenhouses growers are able to maintain precise control over the environment (e.g., temperature, humidity, air quality, lighting, etc.). With the cannabis plant on a 12-hour photosynthesis cycle, it is critical in certain seasons and geographical locations to make up for lost daylight hours and light intensity. The sun might shine brightly in Washington state 14 hours a day in the summer, but the rest of the year supplemental lighting can be a necessity.

In addition to seasonal and geographical lighting changes, weather and particles in the atmosphere can alter the quality and quantity of light. With concerns over changes in global climate patterns and increased energy grid usage, managing greenhouse lighting systems in a responsible manner is more critical than ever before. Current indoor cannabis production estimated at 1 percent of the U.S.’s total electricity consumption per year — what roughly 2 million average households generate. With the industry expected to grow exponentially, the carbon footprint must be taken into consideration.

5 Benefits Of Using LED Supplemental Lights In Greenhouses

If you’re choosing to grow your plants in a greenhouse, you already know how valuable natural sunlight is for your crop. After all, plant life has developed a complex system of biological processes around the signals of the sun. And if you’ve chosen to take advantage of the sun’s specific light spectrum, it makes sense that you would want to choose variable-spectrum greenhouse LED lights to supplement those natural rays. While HID and fluorescent lights are only going to blast your plants with a limited spectrum, LED grow lights help you mimic the wavelengths of the sun . . . especially if you choose a variable spectrum fixture. That way, your supplemental lighting works with the sun.

But while the variable-spectrum nature of LED lights is one of the more obvious benefits, there are several reasons why LED is a great choice for supplemental greenhouse lighting. As you weigh your supplemental lighting options, here are the five most powerful points to put in the “pros” column for LEDs.

Speed Up Your Harvest Cycle

We don’t need to tell you that the faster you usher your plants through their grow cycle, the greater your overall yields and potential profits. If you depend strictly on natural sunlight for cultivation, you’re bound by the slow progression of the seasons. If you supplement with HID lights, you may be able to manipulate your plants somewhat by switching out MD bulbs for the redder glow of HPS lights. But the nuance and variability of a high quality, adjustable LED grow light allows you to create the most true-to-nature seasonal progression possible. You can guide your crop from germination to harvest more quickly than the sun and more naturally than HID bulbs.

LED grow lights also allow you to fit more grow cycles into a year. Even if you live in a darker climate or it’s the dead of winter, the intensity and comprehensive spectrum of LED grow lights allow you to create any season under the greenhouse roof.

Lengthen the Daylight Period Without Losing the Sunrise/Sunset Effect

Light spectrum is not the only benefit to growing in a greenhouse. Your plants are also responsive to the transition signals of sunrise and sunset. When night falls, your crop switches from photosynthesis mode into metabolism. Much like humans, plants use the night hours for growth, putting the energy they created during the day towards things like root development and budding. The gradual glow of sunrise and the waning light of sunset give your crop a heads-up that it’s time to start transitioning from one process to another.

Now, if you use HID grow lights to supplement sunlight, you get to make the days as long as you need them to be in order for your plants to flourish. This is, after all, one of the main reasons greenhouse growers choose to install supplemental lighting in the first place. However, HID lights typically have two settings: on or off. This means that if you’re extending the day beyond sunset hours, your plants lose the opportunity to transition gently from one process into the other. Instead, they’re plunged into darkness, and this can shock their system and hinder growth.

More advanced LED lights come equipped with a sunrise/sunset option allowing you to start and end “daylight” hours whenever you want while still providing your crop with those supportive transitions.

Give Your Plants the Best Possible Light with Variable Spectrum Control

Like the sunrise/sunset feature, this benefit does not apply to all LED grow lights, but it does apply only to LED grow lights.

You will not find variability in HID bulbs. Generally speaking, an HID grow light setup requires you to use MH bulbs for vegetation, then trade that blue-spectrum lamp out for an HPS light that’s heavier on red for flowering. It works, yes. But variable spectrum LED grow lights work far better. These lights allow you to program the exact balance of color that’s best for your specific species of plant at each moment in their grow cycle.

To make things even easier on you, technologically advanced grow lights like the California LightWorks GH Pro 340 feature photo sensors for automatic light balancing. Translation: the grow light adjusts to truly supplement the available sunlight in any given moment. You don’t have to worry about overwhelming your plants or wasting energy on excess light. On brighter days, the lights dim. Between this feature and the variable spectrum control, you can ensure your crop gets only what it needs and exactly what it needs.

Reduce Operating Costs

It’s no secret that lighting makes up a huge percentage of any grower’s energy costs. LED grow lights help reduce those expenses in a number of ways.

First, LED lights are famously more efficient than HID and fluorescent bulbs. The industry-leading brands like California LightWorks offer an efficiency of up to 3.0 micromoles per joule while HID lights have an efficiency of less than 1.9 micromoles per joule. And because variable spectrum LED lights allow cultivators to specify the exact intensity needed per color, you don’t waste energy on wavelengths your plants can’t use.

The use of LED grow lights also allows growers to save on supplemental cooling. These lights emit far less heat than any of the other lighting options, and models like the GH Pro 340 feature passive cooling. Cooler lights also mean less evaporation, which means water goes further in your greenhouse operation.

Finally, as an added bonus, most regions of the United States offer a rebate for greenhouses that switch to supplemental LED lighting, significantly offsetting the cost of the lights before you even calculate energy savings over time.

Enjoy Consistent Light Quality for Years

It takes a lot to keep up a greenhouse. No matter how expansive your operation is, your plants undoubtedly keep you busy enough as it is. So, it’s no small benefit to be able to install your lights and not have to even think about replacing them for 10–15 years.

This is the case with LED grow lights. The highest quality lights have a lifetime rating of over 50,000 hours. For comparison, a good HID bulb lasts at the most, 24,000 hours, and even then, the decline in light quality is significant in as little as 5,000 hours and the bulbs must be changed.

ECO Farm 90W LED Grow Light Bar — Supplemental Lighting

Pros

Passively cooled light bars allow for versatile application
Wet-rated
Easy vertical and horizontal installation
Quality components throughout design
5-year warranty

Cons

Dimmable feature requires use of additional adapter (not included)
Expensive option for home grows

ECO Farm 30W UV & IR Supplemental Lighting Bar

Pros

Top of the line LEDs
Fully programmable
Remote controlled

Cons

Price (but it’s worth it)

Here are some tips and considerations to maximize your supplemental lighting system:

Operation of lamps. Consider when you run your lamps on both a daily and seasonal basis. There is little to no benefit of operating lights when it’s sunny outside. Thus, lamps should be controlled by an environmental control system or a quantum sensor, and not simply run on a timer.

• Operate lamps only at night and during cloudy weather.

• Turn the system off when the average DLI exceeds 10–12 mol·m–2·d–1. For growers in the northern U.S. and Canada, this usually begins in March or early April.

• If you have HPS lamps controlled by a computer, have different on/off settings so there is a deadband, ensuring that lamps don’t repeatedly turn off and on during partly cloudy conditions. Repeated on/off cycles reduces the longevity of bulbs. This is not the case with LEDs, so they can turn on/off based on instantaneous conditions.

Uniform intensity. Crop growth is more uniform when the intensity of supplemental lighting is uniform. When lamps are installed without a specific lighting plan produced by your lighting supplier, intensity can be quite variable. Under higher light, growth is increased and plants dry out faster than plants under less light, which makes moisture management difficult. In addition, non-uniformity during the young plant stage can lead to non-uniformity after transplant.

Replace/clean HPS bulbs and reflectors. The output of light from an HPS bulb decreases as it ages. A standard recommendation is to replace HPS bulbs after around 12,000 hours of operation, when their output is 85 to 90 percent of the original intensity. Although bulb output decreases, they still consume the same amount of energy, so their lighting efficacy decreases while the benefits to crops also decrease. In addition, one out of ten bulbs fail after 14,000 hours of use.

Over time, both bulbs and reflectors get dusty and dirty, which each reduce the amount of light to your crops. Research at Utah State University showed that dirty bulbs and reflectors can each reduce light output by as much as 10 to 15 percent. Therefore, periodically cleaning bulbs and/or reflectors (every year or two) is recommended by most, but not all, lighting companies. Contact them for recommended cleaning methods.

Ensure other factors aren’t limiting. The major “ingredients” to photosynthesis are light, carbon dioxide (CO2), and water, plus adequate nutrition. If CO2, water or fertility are too limited, the benefits of supplemental lighting are reduced. Water and fertility are often managed to suppress extension growth, which is fine, assuming that plants don’t experience nutritional deficiencies, and plants aren’t withheld from water to the point of wilting. CO2 is usually not measured in a greenhouse, but it can become limiting in tightly-sealed greenhouses that are full with plants. In that case, consider periodically bringing in fresh air when lighting, or enrich the greenhouse with supplemental CO2.

Time to upgrade? The efficacy of lighting (the conversion of electricity into photosynthetic light) has increased dramatically in the past few years, for both HPS lamps and LEDs. If you have old HPS lamps, consider upgrading to new fixtures, especially if your electricity rate is high. The most efficient HPS lamps are now at least twice as efficient as older lamps, and the most efficient LEDs are nearly three times more efficient. Run the numbers to determine if an upgrade is a worthwhile investment.

Final thoughts

In a greenhouse environment where sunlight is plentiful for a significant portion of the year, a grower needs to look at a reasonable time span of low light before supplemental lighting kicks in; otherwise they are being used unnecessarily. If a grower is looking for supplemental lighting in order to extend the day length for their crops they should ask themselves the following questions: what time is electricity the cheapest? What are your light level requirements and what time does the crop need supplemental lighting? Consulting the experts to help your determine the answers to these questions will ensure you’re using your supplemental lighting as efficiently as possible with minimal energy waste.