This document provides the methodology to be used by network or facility operators to characterize the energy efficiency of their facilities. This technical report represents one part of the larger ATIS suite of standards concerning Telecommunications Energy Efficiency (ATIS-0600015.xx.YYYY). In contrast to supplemental standards dealing with specific equipment@ this technical report (ATIS-0600015.05) addresses the efficiency of telecommunications facilities and is to be used with reference to ATIS- 0600015.2009. Purpose This document provides a set of definitions@ requirements@ and guidelines for calculating the Telecommunications Energy Efficiency Ratio (TEER) of telecommunications facilities. The TEER ratings defined in this specification provide a common reference that can be used by system providers to indicate the multiplicative effects of power consumption at the facility level. Application This document (and supporting documentation) is intended to be used by system providers to evaluate the efficiency of their facilities. Service providers can use this information to determine what facilities have the highest overhead. Service providers and network operators can also use this information (for a specific facility or averaged across a service provider's facilities) to determine the facility-level impact of equipment-level power consumption. This can be applied to controlled environments in central offices@ network data centers@ controlled environment vaults (CEVs)@ telecommunications huts@ and base stations in buildings.