Compared to the farming of most other crops, commercial cannabis cultivation’s impact on the environment is minimal – except when it comes to power use. A large proportion of cannabis cultivation takes place on indoor grow sites, using man-made lighting arrays as a substitute for daylight. These setups and their accessories, including the fans and HVAC systems that prevent the plants from overheating in proximity to the lights, can demand large amounts of power. Unsurprisingly, areas which have legalized cannabis cultivation have seen corresponding increases in energy use: In Colorado, cannabis grow facilities used 200 million kilowatt hours of electricity in 2014, with cannabis cultivation accounting for almost half of Denver’s yearly increase in energy use. For cities and states planning to legalize cannabis while still limiting their use of electricity, regulating the power used by cannabis cultivation is a must.