Engineering Efficiency: Optimizing Energy Systems in Indoor Cannabis Cultivation Facilities

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As cannabis production continues to increase in the US, focus on efficiency in cultivation has also increased. Indoor cultivation strives to create an ideal ecosystem for cannabis plants, but this effort comes with inherent challenges. Focusing on lighting, climate control, water usage, and air circulation, this article compiles three different perspectives – a scientist, a grower, and an engineer – on how to optimize cannabis growing from an energy usage standpoint while still supporting healthy plant growth.

A study published in 2025 outlined the effects of indoor cannabis cultivation on greenhouse gas emissions and climate change, noting that indoor cultivation increased from about 33% in 2012 to 65% in 2023, as legalization occurred throughout the country (1). Industry-wide emissions are around 44 Mt CO₂ e/year (from both legal and illegal operations), the equivalent of emissions from 10 million cars. Compared to outdoor operations, “cultivating a given amount of cannabis indoors results in approximately 30 times more emissions per kilogram than cultivating outdoors,” the study explains. “When incorporating emissions from all other stages of the life cycle, cannabis cultivated in plant factories is 7 times more emissions intensive.”

Indoor cannabis cultivation consists of several necessary sources of energy: lighting, water and fertilization, climate control, and air circulation, to name some. Each of these sources contains ways to reduce energy consumption while optimizing the grow operation.

Lighting

Lighting technology in cannabis cultivation has evolved to be more efficient over the years, but a balance is needed between energy conservation and providing the plants with the energy they need. As Zacariah Hildenbrand, PhD, partner of Medusa Analytical, and a director of the Curtis Mathes Corporation (OTC:CMCZ) explained in an interview with Cannabis Science and Technology, “If you don’t have enough light intensity, your plants are not going to thrive, and maybe they don’t even survive. If you have too much intensity, you could get photo bleaching.” Plants will need more light in flower phase than in vegetative phase, he adds, which does require increasing the watts regardless. Lighting technology has evolved from metal halides and high-pressure sodium lights to efficient LEDs, he explains, which provide the full spectrum of lighting that plants need yet do not produce as much waste heat.

Using LEDs for lighting is a significant factor in saving energy in other areas, explained Adam Jacques, owner of AgSense, LLC. “As far as saving money goes, there’s nothing that can touch an LED. When you’re looking at the environmentals, you’re halving everything, as far as heat dissipation and humidity issues and those types of things. It fixes so much in the grow without you having to change too much of your infrastructure that financially, it makes no sense to use anything else.” Additionally, he explains, energy audits with a PAR (photosynthetically active radiation) meter can be useful as well. A critical concept in lighting, PAR “encompasses the range of light wavelengths that drive photosynthesis, typically between 400-700 nm,” as explained in the January/February Cultivation Classroom Column co-authored by Hildenbrand, Hannia Mendoza-Dickey, and Robert Manes, in Cannabis Science and Technology (2). “PAR is quantified in µmol (micromoles) per square meter per second, representing the number of photons within the PAR range reaching a given area in a specific time frame,” the authors explained. PAR meters can help identify hot or cold spots in lighting and ensure an even PAR over the canopy. Also important to note, different genetics will require different levels of lighting, Jacques adds.

At the same time, the energy conservation from lighting can only be taken so far. As Nadia Sabeh, PhD, president and founder of Dr. Greenhouse, explains, the law of diminishing returns applies to cannabis cultivation. “There’s going to be a point at which [the lighting] efficacy that we’re driving towards, micro moles per joule, is going to reach a limit, because there’s only so many red diodes that we can use to grow a plant. We’re going to hit a ceiling at some point.” Occasionally she sees growers negate the energy saved from more efficient lights by increasing light levels or adding more light fixtures to increase plant production, which in turn requires more air conditioning. She offers other options for optimizing lighting in an indoor facility, namely dimmable fixtures, ideal distribution of light, and the greatest use of white surfaces to reflect photons back to the leaves.

Climate

Climate control in indoor grows is another significant source of energy. Combined with lighting, managing temperature and humidity comprises about 70 to 75% of the cost to cultivate, explains Hildenbrand, and though HVAC systems are a significant initial expenditure, they are crucial for maintaining the vapor pressure differential (VPD). “You’re trying to be in an optimized range of temperature and humidity, where the plants are happy, not too hot, not too humid, not too dry, not too cold,” he explains. Energy usage of the HVAC system is about equivalent in amount of energy as lights, Sabeh explains, though it can be slightly less because while the HVAC system is removing energy generated by the lights, some light is converted into plant biomass through photosynthesis. Some HVAC systems use hot gas reheat to recover the heat of compression. For systems that do not, an additional heat source—electrical or gas—will need to be used, Sabeh added, which results in higher energy, possibly more than from lighting.

Additionally, negative air pressure in smaller grows may even be enough to offset the heat generated from LEDs, Jacques explains. When looking at insulating the operation, building construction and location needs to be taken into account, such as wood or steel frame, potential radiant heat, and region climate, for example. Jacques explains he has found spray foam to be the easiest because it avoids mold issues other insulations can cause due to the humidity in the facility.

Insulation for most indoor grows are at an R rating between 10 and 30, depending on climate zone and region, explains Sabeh. Every inch of an insulated panel represents R5, so a four-inch-thick structural insulated panels (SIP) which would represent R20, and a correct building envelope would add R10 to equal R30. “You need to make sure that you are meeting your local building codes,” she adds. “Because every state, even local jurisdictions within states, use a different energy code or mechanical code. As time has moved on, those R values have mostly increased.”

Water

Similar to lighting in indoor cultivation, water conservation also has its tradeoffs. A fully closed loop system can theoretically reduce water consumption and loss by recirculating it, though managing the recycled water can be challenging. Hildenbrand explains that the cost to filter the recaptured water is something to consider, especially depending on your soil matrix. Nutrients like nitrogen, phosphorus, and potassium need to remain part of the soil, though the soil could also contain heavy metals or other contaminants that need to be removed. A reverse osmosis filter can be used, yet it is inherently energy intensive, he adds.

Jacques notes that UV lighting or activated carbon filters are being used by some growers. “What we’re trying to do is get that water back down to a zero PPM state,” he states. Consistency is also a must, he adds, though the overall payoff of the system needs to be taken into account. “Once you start paying for all of these things to keep your water clean in a closed loop, you’re throwing the baby out with the bath water because you’re spending so much additional energy and money and time to reclaim this water.” Closed-loop systems may be less feasible for smaller operations, and also depend on your location, Jacques explains. Water scarcity issues or hydroponic grows with drip lines are examples to consider when weighing water conservation. “I want to save as much natural resources as humanly possible, but with something like a closed loop watering solution, I would say that your money could be spent better somewhere else in the process,” he explains. “You can do it, it’s great long term water care if you’re willing to do the investment. At a corporate scale where you’re growing an acre of closed loop indoor greenhouse, that might start making a lot more sense.”

Sabeh also advocates for careful water consumption methods that do not generate waste. She explains that currently, with reverse osmosis, nutrients and fertilization need to be added back into the recaptured water, the pH may need to be rebalanced, and at most 70% of the water is recaptured. Ultimately, she states, energy can come from renewable resources, but fresh water is a limited resource and focus on reducing its consumption across agriculture in general is important.

Air Circulation

Air circulation is a crucial component of maintaining VPD, Hildenbrand explains. Structural engineers can assess facilities and recommend improvements that can make a significant impact, he explains. Sabeh emphasizes design over technology with air circulation efficiency. To avoid hot spots, she recommends the traditional horizontal airflow fans (HAF) air circulation strategy, common in greenhouses, using the racetrack design to create a funnel to pull hot air to the plant canopy. She cautions against vertical air flow because when cannabis is being grown densely, it can result in low velocity and air becoming trapped on top of the canopy. Likewise, under-bench airflow can be inconsistent and increase the transpiration rate of the plants, increasing their water intake and reducing water conservation.

The air exchange rate is going to be different for each grower, Jacques explains, depending on the volume of the space. Wall-mounted oscillating fans in a grid pattern can help reduce dead spots, and using negative pressure through an extraction fan can be an added help with cooling in space with no open CO₂. Implementing environmental sensors can help adjust power usage in real time. “The fans go on to X amount of speed when we hit X humidity or X temperature,” he explains. “So instead of running all of your HVAC and dehumidification and fans at the same level all the time, we can use some sort of controller to have those change their power usage based on what’s specifically happening in the room at that point.” Manual or automated energy audits that track highs and lows of humidity and temperature and adjust as needed can also help optimize energy usage, he adds, saving on electricity bills.

Final Thoughts

According to Sabeh, when monitoring the environmental conditions of a grow operation, placement of a sensor such as a thermostat or relative humidity sensor is crucial and must be representative of the environment as this affects the energy efficiency of the equipment. Another common impact on the environment Sabeh sees in facilities is doors being left open. “I can look at a data set, a plot, a graph, and I can point out almost every single time when the doors were open, because you see a rapid change in that environment.” This also exposes the plants to mold spores.

Hildenbrand says that it’s important to advocate for environmental stewardship and be a good neighbor to everyone on the same power grid. “If you can afford the initial capital expenditure of solar panels and you live in a favorable locale, you should absolutely go that route as a supplemental measure,” he explains.

Jacques warns that while there are important measures growers can take to maximize efficiency and create an ideal environment, some things may be out of one’s control. “The plants have a mind of their own, believe it or not, and they’re going to do what they want to do,” he explains. “It’s like raising a kid, right? Every genetic is different. They’re not going to react the same to your environment, your watering schedule, your nutrients, and so it’s just trying to build the best environment you can so they can become themselves.”

References

1. Mills, E. Energy-intensive indoor cultivation drives the cannabis industry’s expanding carbon footprint, One Earth. 2025. DOI: 10.1016/j.oneear.2025.101179
2. Hildenbrand, Z., Mendoza-Dickey, H., Manes, R., A Call for More Representative Horticultural Lighting Metrics for Cannabis Cultivation, Cannabis Science and Technology, 2025, 8(1), 14-19.

How to Cite this Article

McEvoy, E. Engineering Efficiency: Optimizing Energy Systems in Indoor Cannabis Cultivation Facilities, Cannabis Science and Technology, 2025, 8(2), 24-26.