This paper deals with the problem of minimizing waste heat loss in a small-capacity gas turbine using a low-boiling fluid (LBF) circuit working in organic Rankine cycle (ORC). In this study, firstly, we have developed an approach for calculating the heat-and-mass balance for a power installation with a heating fluid. Secondly, we have carried out calculations of installations with various working fluids and analyzed the main characteristics. During the study, four working fluids were taken into account: butane, pentane, R245fa and cyclopentane. The study shows that the working fluid should be selected not only depending on its critical temperature, but taking into account the influence of the weight and dimensional characteristics of the steam generator. Ultimately, working fluid selection is both a technological and economic problem.