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When you hear the buzzword marijuana (aka "pot", "weed"), you probably start thinking about some of the big issues regarding the well-known drug: history, health effects, legalization, etc. But you may be surprised (as I was) to find that the latest concern surrounding pot is energy consumption.
 Like most plants, cannabis sativa (the marijuana plant) takes a considerable amount of energy to grow. When this energy comes from the sun, it's no problem. But put these babies in a grow house under artificial lights and suddenly the operation becomes a major electricity hog.
Grow houses are basically homes converted into places specifically for growing cannabis. In most U.S. states, it is illegal to grow and sell marijuana, so the grow house provides the advantage of secrecy for those who would go against the law. You might think then that legalizing the sale of marijuana would move many indoor operations outside. But that law was passed in Colorado in January, and since there has actually been a sharp increase in new grow houses.
This increase creates a sizable increase in electricity consumption. After all, the controlled atmosphere of a grow house requires a lot of energy. Most of the energy demand is from the artificial lighting that replaces energy from the sun. The rest is from other processes such as dehumidification, cooling, heating, and ventilation. The power use at some large grow centers is comparable to a high-end data center. The operations (legal and illegal) account for around $6 billion in electricity annually in the U.S.
And while energy reduction in homes is often as simple as switching from incandescent to LED, where plants are concerned, there's more to consider. Varying wavelengths of light may affect the way that plants grow, a topic being investigated by senior research scientist Tessa Pocock at Rensselaer Polytechnic Institute. Some high intensity LED grow-lights are also either very expensive or lacking in efficiency compared to other types of bulbs.
 The alternative to grow houses is greenhouses, which to me makes much more sense. Apart from perhaps the security benefits, there seems little to be gained using the grid's energy over the sun's. And if marijuana acceptance does continue to grow, the concern over energy consumption will grow with it.
Sources
MIT Technology Review - Weed's Chronic Energy Use Becomes a Concern
RIT News - LRC Launches Plant Lighting Program
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