The ongoing wave of state-by-state cannabis legalization is creating radical transformation in many ways. One often-overlooked aspect of this trend is the impact on electricity usage and resulting new load pressures on the grid, particularly in the often remote and rural regions where cannabis production is ramping up.

Cannabis production may be getting most of the headlines, but it is only one part of a broader shift in how and where we grow agricultural products. The rising farm-to-table movement and heightened concerns over food safety are driving demand for more localized production in rural areas, which have widely varying growing seasons and other climate factors.

The upshot is that more and more agriculture production — including cannabis — is being shifted to greenhouses and larger production factories, contributing to new demands on the power delivery system.

Cannabis Production is Spreading

With 33 states and the District of Columbia legalizing cannabis use in some form, production is increasing exponentially. While the majority of those states have passed laws allowing medical usage, a growing number are also allowing recreational use.

Due to climate and prohibitive costs for indoor production in states where cannabis is legalized, about 90% of cannabis grown in the U.S. is done so outdoors. In Tennessee, Kentucky, Hawaii and Washington, outdoor production is close to 100%. 

In Oregon, the method of production is more balanced with 55% of production outdoors. Montana is at the other end of the spectrum, with only 20% outdoor production. 

Most states mandate a certain level of security on the growing operations, which creates additional pressure on producers to set up indoor facilities where production can be tightly controlled. This is occurring even in states where climate conditions are relatively favorable for outdoor production.

Power Demand is Spiking

According to a 2014 study from the Northwest Power and Conservation Council, hundreds of producers in Washington have been licensed to process cannabis. Growers of cannabis create new power demand ranging between 80-163 megawatts (MW) on the Northwest region's system. According to the latest data available, the Northwest Region accounts for approximately 21% of production within the U.S., with an estimated 18% from Washington. 

Using these figures, we can estimate that total power demand for cannabis production throughout the U.S. ranges between 381 MW and 776 MW. It is likely this power demand could grow even more within the next two to three years as production ramps up in states that have recently legalized cannabis. 

This amount deserves special attention from electric utilities, especially as more states legalize cannabis and demand continues to grow. Even though only 10% of cannabis in the U.S. is grown indoors, the load profile for cannabis plant factories is far from flat, varying from 4 to 20 kilowatts (kW). Indoor growth requires 5,000 kilowatt-hours-per-kilogram (kWh/kg) of production and lighting alone accounts for 80% of electricity use. 

Production load is driven by the crucial need for lighting for optimal growing conditions.

The vegetation room requires a 1,000-watt metal-halide lamp for every two to eight plants, with lamps needing to be on for at least 18 hours per day. The flowering room requires a 1,000-watt high-pressure sodium adjustable ballast lamp for every two to three plants and needs to be on for 12 hours and off for 12 hours.

In addition to lighting, the heating, ventilation and air conditioning (HVAC) systems need to be set precisely with temperature and humidity set points required for each growing room in addition to an air conditioning mini-split for every 1,000 square feet. 

Of course, utilizing more energy-efficient lighting can play a crucial role in reducing power demand, and as power costs decline the economic incentive increases to switch from outdoor to indoor, and more controlled production. 

Within Washington, we calculate that switching to more efficient lighting has the potential to generate demand savings of 23 MW by 2020 and 36 MW by 2035. However, the economics of switching to more efficient lighting may impact these calculations as it must be noted that more efficient LED lighting is more costly than conventional lighting.

Absent demand-side incentives available from local utilities, it is likely that only large-scale growers will be in a position to absorb the additional costs of more efficient and less power-intensive lighting.

Agricultural Transformation

Cannabis is only one part of a nationwide transformation in how agricultural products are produced.

Traditionally, seasons and weather have dictated what crops are grown where and when. For instance, strawberries are grown in California and salad ingredients are grown in Mexico during the winter. However, greenhouses and food plants are increasingly being introduced to the food production process as a means to bypass adverse seasonal limitations in regions outside of California and Mexico.

In traditional U.S. agriculture, produce travels an average of 1,400 miles from remote locations to urban centers. With mounting concerns over climate change, there is growing attention to the fact that shipping 1 ton of produce generates 500 pounds of carbon dioxide (CO2).

In addition to climate concerns, a growing number of consumers are demanding more locally produced food products in support of the burgeoning farm-to-table movement and out of concern over food safety of products shipped over great distances. 

Greenhouses Versus Plant Factories

Consumer demand for locally grown food is driving more food production toward greenhouses and plant factories.

A factory is defined as a facility that grows plants in a much more controlled environment than greenhouses. In most cases, the factory uses hydroponics to grow plants with modern LED lighting and typically uses shelving units that may extend a considerable distance vertically with lighting installed on the bottom of the shelf above each row of plants. Indoor cannabis production often utilizes similar plant factory setups.

Greenhouses are far less costly to operate than plant factories, generally because they are less energy intensive. With light and heat coming from free passive solar energy, the cost benefits of conventional greenhouses can outweigh the need for full climate control in certain growing regions.

However, greenhouses in the most extreme weather locations are not viable without aggregating features of plant factories, such as artificial lighting and active heating or cooling.

As agriculture moves farther from an ideal climate for a plant species, the need to move first to a greenhouse and then to a plant factory becomes more urgent. Even plant factories that are not optimized for a minimal energy or environmental footprint can be cost-justified due to higher production-per-unit profiles, particularly if they are located in densely populated urban areas.

Moreover, the better the efficiency of the lighting system, the more plant factories are likely to be used on a purely economic basis.

Accurate Projections Needed

The likelihood that more cannabis production will come from plant factories, combined with shifts in food production toward factory settings, means utilities must make more accurate forecasts for these new types of load. These loads may vary widely, not only in average load size but also in load profile.

The main similarity in all plant factories is the relative power demand for artificial lighting. As lighting efficiency is increased — even by a factor of 7% or 8% — a major shift from greenhouses to plant factories is likely to occur.

The dual trends of cannabis legalization and changes in consumer demand for types and origin of produce are changing the trajectory of the agriculture revolution. 

Electric utilities nationwide are investigating some of the effects of these changes to the power grid. An effort to continue quantifying these changes is needed in the short and long term to help utilities better prepare for the future.