It may be argued that society is becoming increasingly demanding for the quality from any activity. Even if it is true it is not easy to assess the quality of various processes as popular economic criteria hardly comply with the concept of sustainable development. Exergy, as an objective indicator of used and transformed energy quality, is used for the evaluation of energy transformation processes in different areas, such as: biology, technology etc. It is not affected by inflation, devaluation, and crisis. The compromise of combination of exergy and economic criteria is defined by exergoeconomics. This paper presents theoretical basics of exergy and exergoeconomic analyses. The exergy and exergoeconomic analyses were performed for 20 MW thermal capacity combined-cycle cogeneration plant. The exergy analysis allowed the identification of elements where the largest exergy losses are formed. The exergoeconomic analysis was conducted to determine costs of such system imperfection economically. Additionally, costs of final products (e. g. heat and electricity) were calculated.