The challenge for every grower in today’s hyper-competitive environment is how to optimize profit and adjust their methods to stay competitive or get an edge.
One of the major profit decisions for indoor cultivators revolves around the best way to replace the sun. Cannabis loves intense light. This led to the discovery that high-pressure sodium (HPS) lights were effective at generating this kind of intensity. However, HPS technology requires excessive power and more than half of the energy is dissipated in the form of heat into the grow room.
Today, HPS lights are still very competitive in certain situations but LEDs are beginning to replace older technology for a slew of reasons. The total investment and operating cost of your lighting system will depend on operating voltage and current draw, wattage (the amount of power consumed by the lights), the amount of heat generated and how much automation is used.
Voltages can be tricky, so it’s important to talk to an electrician. The choice of voltage has a huge impact on initial building costs.
Generally speaking, the higher the voltage, the lower the current draw (fewer amps). This also makes it easier to install electric wiring, while keeping the power company happy. Wiring and circuit breakers are limited by the amperage. As your company expands, so will its current demands.
But once a facility hits the limit of its circuits, the number of grow lights that can be installed is limited. So choose carefully.
Here’s an example: Let’s say you want to use a 1,000-watt HPS light. This grow light uses the most power draw and often has 115% boost mode, whereby it uses even more amperage. While the actual alternating current (AC) voltage may be as much as 10% lower than nominal value, the system has to be designed to handle the maximum current draw.
As the table above shows, if the nominal AC voltage is 120 volts, it could draw as much as 11.5 amps, which means only one of these lights can be connected to the circuit breaker. As AC voltage is increased, the lights start drawing less current.
As the voltage is increased to 480, an HPS grow light will draw 2.7 amperes, which means seven lights can be connected to a breaker on a per-light basis, but would still be at the same power consumption and light output.
Wattage will determine how much power grow lights consume — and how much it will cost to operate them.
For example, running a 1,000-watt HPS light with about 1,050 watts of actual power draw for 12 hours a day will consume 4,600 kilowatt-hours (kWh) a year. That same light intensity can be achieved with lower-powered LED bars mounted close to the canopy, resulting in a savings of more than 2,000 kWh over that same period.
There’s also a big difference in heat generated between HPS and LED lights. This matters because heat will likely need to be removed via air conditioning — another expense that needs to be considered.
In North America, heat is measured in British Thermal Units (BTUs): 1 watt is equal to 3.41 BTUs per hour.
In an indoor growing space, all the electrical energy drawn from the mains ultimately turns into heat in the room, with one key exception: the less than 1% of the energy that becomes useful chemical energy (biomass in your plants) in photosynthesis. The remainder turns into heat and increases the temperature in the room.
By converting the input wattage to BTUs, a grow light that produces 1,080 watts will result in 3,682 BTU/h of heat.
That can be a good thing for an operation in a cold environment, but most facilities are going to need to remove some of that heat.
The concept is the same with lower-power LEDs, but the numbers change a bit. With LEDs, the downward infrared radiation is much lower, so the lights can be placed closer to the plant canopy, meaning a higher percentage of photons will hit the canopy. Ultimately, cultivators get the same results, but they will draw a lot less power from the mains, while generating less heat.
Air conditioning is another key cost that should be managed carefully to minimize expenses while protecting plants. The amount of cooling needed is often expressed in tons. One ton of cooling equals 12,000 BTU/h. That’s enough to handle three HPS lights or about six LED lights.
Cooling efficiency is needed in order to project air conditioning costs. This is best measured by the seasonal energy efficiency ratio (SEER). Ask a heating and air conditioning or insulation expert about the SEER of your building. It can also be calculated by dividing heat output by the electrical power of your air conditioning.
For example, with grow lights that generate 1,900 BTU/h and an air conditioner that consumes 100 watts, the building’s SEER would be 19 BTU/watt-hour.
So how can air conditioning needs be figured out from this information? Let’s say you have a well-insulated room, 10 HPS grow lights operating 12 hours a day for 365 days a year, a warm climate and a SEER of 15. This setup would produce a heat output of 36,820 BTU/h. If we divide this by the SEER rating of 15, we get 2,455 watts. This is the power required by the air conditioning and the total energy consumed would be 10,753 kWh.
By comparison, the grow lights themselves will consume the lion’s share of costs — 47,300 kWh during this same period.
But air conditioning costs can be minimized by careful planning. When you keep in mind that the system must be designed for the peak load, you can control air conditioning costs through scheduling to ensure that not all your grow lights are on at the same time. If you have a 100-LED lighting system that generates 190,000 BTU/h when they’re on for a 12-hour period, that would require 16 tons of cooling. But if the lights are equally distributed to two different grow rooms, one can be operated from 8 a.m. to 8 p.m., while the other runs from 8 p.m. to 8 a.m., then an eight-ton air conditioner will suffice.
There’s a lot to consider when investing in your grow light system. The great thing is that by using some simple tools, such as the lighting cost calculator on AEssenseGrows’ website, you can quickly make an intelligent business decision and maximize your profits in the process.
The new installation and replacement market for cannabis grow lights in the U.S. is estimated to be $76 million in 2018 and $112 million in 2023, according to estimates originally sourced from New Frontier Data’s “US Retail Sales Projections” and adjusted according to trends analyzed by AEssenseGrows.
That’s a lot of lights, and cultivators are faced with a wide range of options. Indoor farming delivers great control, but at a significant cost, so selecting the wrong lights can be detrimental to your plants and the bottom line of your company.
Phil Gibson is the vice president of marketing at AEssenseGrows. He has been with the company since 2016 and manages business development and marketing globally for indoor cultivation. He has a master’s degree in business from the University of Southern California and an electrical engineering degree from UC Davis. A detailed white paper addressing the total cost of lights can be found on the AEssenseGrows website.