An exergy balance for an industrial glass furnace was constructed on the basis of measured thermodynamic variables. The experimental data were collected for different operating modes, especially in relation to oxygen enrichment. Losses were classified as belonging to one of three categories: 1) chemical reaction, 2) dissipation of heat (by radiation or sensible heat) to the environment, 3) heat transfer. Using this method, optimum conditions, with reference to oxygen enrichment of the combustion air, can be determined and the processes where the bulk of input exergy is destroyed can be identified. These results allow the designer to select modifications to furnace design and/or changes in operating modes that will be effective in enhancing plant efficiency. The last step is a thermoeconomic cost evaluation of the tested plant.