Does it make economic sense for you to install grow lights?

The Lighting Approaches to Maximize Profits (LAMP) project aims to determine how growers can maximize their return on investment when considering installing grow lights.

As light emitting diodes (LEDs) become more efficient and more affordable, an increasing number of greenhouse and plant factory growers will consider installing LED luminaires to light their crops. In the case of greenhouse growers, these luminaires would provide light to supplement natural sunlight. For plant factory growers, production depends entirely on the light provided by an artificial light source including LEDs, high pressure sodium or metal halide luminaires.

According to University of Georgia horticulture professor Marc van Iersel, the electricity for supplemental lighting in a greenhouse accounts for 20-30 percent of variable costs. In the case of plant factories which rely solely on artificial light, the electricity cost accounts for 50-60 percent of the variable costs.

van Iersel is heading up a $5 million, four-year research project that will focus on enabling growers to maximize the return on their lighting investment. Funding for the Lighting Approaches to Maximize Profits (LAMP) project is being provided by the USDA National Institute for Food and Agriculture Specialty Crop Research Initiative. The team that has been assembled to work on the project includes 15 university researchers, an advisory panel of greenhouse and plant factory growers and industry consultants.

“The job of the advisory grower panel is to make sure that the research that we do is actually what they need,” van Iersel said. “These are growers who will directly benefit from the research. We are also working with consultants who represent a big section of the industry. We are looking to them to help disseminate the information generated by the research to the industry.

“The research is looking to determine how growers can maximize their return on investment. There has been a lot of research done on how to grow plants with LED lights. We know growers can produce plants with lights. But what we don’t really know is how can growers make the most money doing it.”

Focused on LEDs

van Iersel said most of the project’s research will focus on the use of LEDs with some economic comparison to high pressure sodium (HPS) lamps.

“LEDs are clearly the lights of choice for the future,” he said. “Where we are interested in comparing LEDs and HPS is in regards to the economics. LEDs are more efficient, but they are also more expensive. Is the extra cost of LEDs worth it or are some growers actually better off paying less in capital expense for HPS lamps and more for the electricity to operate them? That is not a simple question to answer.

“There really hasn’t been a big price drop in LEDs. What LED manufacturers have done is rather than lowering the price, they have focused on making the LEDs better. Newer LED lights have hundreds of individual diodes in them. That is one way to help make the lights more efficient. But obviously they are putting more hardware in the lights. In older LED lights there were fewer individual diodes that went into a single light. The diodes were expensive. Now that the diodes are relatively cheap the manufacturers are putting in more of them so that the lights are more efficient. There seems to be a race among manufacturers to try to make the most efficient LED light possible. Right now it seems like the focus is more on creating a more efficient light than on creating a cheaper light.”

van Iersel said LED light manufacturers can easily match the light intensity of HPS lamps.

“What the LED manufacturers typically do with more diodes is run the diodes at only a fraction of their full power,” he said. “That makes the diodes more efficient. If an LED operates at 50 percent of its maximum power, it is substantially more efficient than running it at full power.”

Using supplemental light efficiently

One area that van Iersel is particularly interested in studying is making sure that growers provide supplemental light when plants are best able to efficiently use the light.

“LEDs are fully dimmable and can be dimmed instantaneously,” he said. “LEDs can very easily be programmed to respond to ambient light levels. One of the things that we are working on is designing systems that dim automatically as the sunlight level increases.

“With LEDs it’s more than turning them off and on, it’s dimming them. We have a system where we are calculating every second how much light to provide and how much to dim or brighten the LEDs. That is not possible to do with HPS.”

van Iersel said most LEDs are already dimmable.

“Every LED light is dimmable, it’s just a matter of using the right driver, which provides the power to the LEDs,” he said. It is very easy to incorporate into the lights. What I would hope is going to ultimately happen is growers are going to demand this kind of technology when they look at LEDs and the manufacturers have no choice than to provide it.”

van Iersel said another area of interest with the research is using the light spectrum as a way to manipulate quality.

“This could be accomplished with either the red:blue ratio or the amount of far red that is incorporated into the spectrum,” he said. “We also want to look at how the light is actually delivered to the plants. Right now, at least with ornamentals, growers look at the daily light integral (DLI) that is required to grow a particular crop. There are some clear indications that if the DLI is spread out over a longer photoperiod, for example, 20 hours instead of 14 hours, with the same amount of light over the entire day that more growth occurs with the longer photoperiod. This would be a lower instantaneous light level, but the same amount of light over the course of the entire day. This would allow growers to purchase fewer lights.”

Simplifying growers’ choices

van Iersel said one of outcomes of the research project is to be able to provide growers with a simple to use calculator that allows them to figure out if supplemental lighting will actually pay back in their particular production situation.

“If we can prevent growers from buying lights if they are not going to realize a return on investment that is going to be a good thing,” he said. “If they do decide that they want to use supplemental light, what makes more sense? Is it better to purchase HPS or LEDs? Which lights are going to offer a better return on investment? We hope to develop spreadsheets and some of this information will be incorporated into the Virtual Grower software program that is available free to growers.”

Current, powered by GE, Arize Lynk LED grow lights are being used by mGardens in its vertical farm in Gorham, Kan.

van Iersel also said some of the information that has been incorporated into the proposed horticultural lighting label is going to be required for the calculations.

“The lighting companies typically provide this information already, specifically the efficacy of the lights. Every reputable lighting manufacturer will be able provide this information. After the LAMP research is completed, growers should be able to look at the label information from different lighting companies and run some scenarios to tell them which lights are the most cost effective for them. It is really difficult right now for growers to decide whether or not to light and what kind of lighting is cost effective. It depends on a number of factors including where they’re located, their electricity prices, the crops they’re producing and how well those crops respond to supplemental light. Unfortunately, currently there is a lot of information that needs to go into doing these calculations. This has hampered the adoption of LED lights because growers can’t determine if they can pay for them.

“Once the research is done, the only numbers growers should need to plug in are basically the profit margins on their crops. Hopefully we will be able to provide them with the rest of the information they need to determine whether installing lights makes sense financially.”


For more: Marc van Iersel, University of Georgia, Department of Horticulture, Athens, GA 30602; (706) 583-0284;;;

This article is property of Hort Americas and was written by David Kuack, a freelance technical writer in Fort Worth, TX.