Small and medium size enterprises (SMEs) have an important role in the Turkish economy because of the workforce involved. According to the size of the industrial facilities, there are different cost components related to the total production costs. Energy cost is usually a small portion of the total production cost, but the Turkish industrial sector comprises approximately 35% of Turkey's total energy consumption and 98.8% of the total number of enterprises in Turkey constitutes the SMEs. Because of the uncertainty of energy costs in the world, it is important to take preventive measures to reduce energy costs and increase efficiencies in industry and consequently in SMEs. In this paper, medium sized enterprises are taken into consideration essentially. Because of getting homogeneity, enterprises with the number of workers between 100 and 200 in the metallic goods industry have been considered in the survey. Energy management includes increasing the profitability by reduced operational costs, and it is also a potential for improving market share. Many different evaluation models have been published in the energy management literature. However, there have not been so many systematic approaches to compare the relative efficiency of the systems. Data envelopment analysis (DEA) is a special linear programming model for deriving the comparative efficiency of multiple-input multiple-output decision making units (DMUs). An evaluation of energy efficiency in 20 medium sized companies has been conducted, and the results are discussed in this paper. (c) 2006 Elsevier Ltd. All rights reserved.