This Recommendation aims to provide a better understanding of the energy efficiency of mobile networks. The focus is on the metrics and methods of assessing energy efficiency in operational networks. Networks are considered whose size and scale could be defined by topologic, geographic or demographic boundaries. This Recommendation explains how to extrapolate the measurements made on partial networks to the level of the total network. Such a simplified approach is proposed as an approximate way of making energy efficiency evaluations at the level of network elements and cannot therefore be considered sufficient for the whole network operation including, for example, transport.