Imperial Codified Standards for Power Plants and Transmission Routes was a book published by the Galactic Empire that set forth standards for the structural engineering of power plants and transmission routes. Facilities were divided into six different categories based upon considerations such as the size of a facility, its sustainability, the amount of power that a facility was capable of generating, the demand for energy by civilian and military organizations and how the energy was ultimately put to use. Two of the six categories were "Fortress" and "Citadel class," with the latter being the largest known category.