The paper examines key issues in improving the energy efficiency of freight rail transportation, crucial for reducing operational costs and enhancing environmental sustainability. The focus is on analyzing factors influencing wagon resistance to motion, a major determinant of train traction costs. Despite its importance, this issue receives insufficient attention in current railway transport optimization approaches. To address this, the paper proposes an energy efficiency indicator reflecting specific energy consumption (in megajoules) per 104 t·km net. This metric enables an objective assessment of design solutions and operating conditions. Various factors affecting this indicator are analyzed, including speed, track infrastructure design, bogie type and construction, as well as axle load and wagon tare weight. The experimental calculation method relies on data from wagon resistance tests. The results show that design features, such as tare weight, axle load, and chassis configuration, can lead to significant differences in energy efficiency – exceeding 40%. This underscores the need for a tailored approach to wagon design that considers these parameters. The authors conclude that integrating the proposed energy efficiency indicator as a key evaluation criterion for wagon development, testing, and operation is essential. The findings aim to reduce energy consumption, enhance rolling stock performance, and promote innovative technical solutions for improving rail freight efficiency.