The production process of glass consumes a high amount of energy, due to the high temperatures in the process. In this work the glassworks Stölzle Oberglas in Köflach was considered energetically with a holistic and systematic approach. The production process was described detailed and based on this, the energy flows were visualized in a process picture. Due to insufficient data, it was not possible to calculate an energy balance for the manufacturing process of glass and so a guideline for recording the missing data and for balancing the individual aggregates in the manufacturing process was designed. Based on available data, unused waste heat potentials of exhaust gases were evaluated, which accrue during the manufacturing process. In addition, recommendations for measures to increase the energy efficiency in the glassworks Stölzle Oberglas were developed.