The paper presents a novel concept for thermodynamic evaluation of a selected energy system. The presented method has been developed by integration of the Thermo-Economic Analysis with the theory of Thermo-Ecological Cost. It can be applied as a thermodynamic evaluation method of rational resources management within any production system. It takes into account both the interrelation of irreversibility within the analyzed system and its influence on the global effects related to the depletion of non-renewable natural resources. The proposed method has been applied to evaluate the production of electricity in the process of natural gas transmission at pressure reduction stations. The expansion system is based on an existing plant integrated with a CHP module, characterized by a performance ratio of 89.5% and exergy efficiency of 49.2%. Within the paper, this expansion plant is supplied with natural gas transported from a natural deposit through a case-study transmission system with 4 compressor stations. The TEC (thermoecological cost) method was applied in conjunction with thermoeconomic analysis. As a result, TEC of the electricity generated in the expanders was determined at 2.42 kJ/kJ, TEC of electricity from the CHP module is 1.77, and the TEC of medium-pressure natural gas distributed to consumers is 1.022. (C) 2014 Elsevier Ltd. All rights reserved.