The city of Austin has numerous green building provisions within the city building code, with requirements that vary according to location, zoning designation and building type. The building standards rely on the Austin Energy Green Building Rating system and the LEED certification system as metrics. In some cases, developers have the option of achieving compliance under either of the two systems. Under the Austin Energy Green Building Rating System, buildings are awarded up to five stars depending on the number and breadth of green building elements that are incorporated into the design. In terms of energy efficiency, rated buildings are designed to exceed the Austin Energy Code.