Expenditures on the charging materials used in an EAF + LF system at a steel plant in Turkey are optimized with allowance for different thermo-economic indices and different combinations of electric-arc furnace (EAF) and ladle furnace (LF). The EAF and LF are regarded as a single system, and the mass balance for the raw materials is determined based on literature data and company catalogues. Cost functions based on energy and exergy indices are constructed to perform the optimization. Constraints on the functions are introduced, the exact constraints depending on the chemical composition of the raw materials and other materials charged into the system, the system's productivity, the maximum amount of energy that can be used, and other parameters. The computer program WINQSB - which is well-suited for the solution of such problems - is used here because the changes in the parameters of the system are linear.