Energy used for growing plants indoors ranges from very small to very large, facility type, and crop. Indoor crop production is inherently more energy use intensive than outdoor cultivation due to the use of systems to control the growing environment. Systems used in vertical farms, plant factories, and cannabis facilities are much more energy intensive, requiring supplemental lighting for 12 or more hours, large air conditioning units to remove both sensible and latent heat, and large fans to achieve high air exchange rates. Understanding energy use in indoor plant production will allow the identification and implementation of energy efficiency measures.