Thermo-ecological cost (TEC) is the approach, proposed originally by Prof. Jan Szargut at Silesian University of Technology (Gliwice, Poland), to evaluate the sustainability of energy conversion and utilization processes thorugh a sound engineering thermodynamics approach. TEC extends the potential of exergy, LCA and exergo-environmental examining also the problem of scarcity of natural resources and identifying the correct path to sustainable development. During the seminar, the TEC method will be presented, followed by the examples of its application in the assessment of contemporary and novel energy systems.