© 2013 IEEE.Power plants plays an important role in term of economic and social affect in all societies. Most of economic sectors and manufacturers are depended in the outcome of power plants in one side and electricity is a vital need of all households and entire society. Therefore, the performance of power plants and consequently their sustainability is crucial concept in the current century. This article proposes a generalized efficiency measurement model for multi-plant firms in terms of returns to scale and number of outputs. This yields to some new indicators for efficiency measurement in an un-communal and communal environment for the local and global analysis. The idea is explained by providing a graphical illustration and numerical example. Proposed models are used for energy efficiency analysis of 46 power plants of 19 provinces in Iran. Local and global aspect of energy efficiency are investigated by using proposed models for aforementioned case study. Primary results are shown that, higher potential energy saving in the communal global environment compared with the local analysis. This highlight the corporation of production electricity units, namely, power plants in this study is a requirement for sustainable energy supply.