The overall efficiency of ORC systems depends on a number of factors, but it goes without saying that the efficiency of the expansion device is one of the most important ones. The article presents the impact of modernization of the first stator stage of a micro turbogenerator on the following efficiencies: exergetic efficiency, Carnot efficiency, microturbine internal efficiency and ORC cycle efficiency. The thermal and flow characteristics for three heat exchangers (i.e. condenser, evaporator and regenerator) were shown. The paper also includes the graphs presenting the current, voltage and electric power generated by the turbogenerator during its operation in the organic Rankine cycle with regeneration. A low-boiling fluid was used as the working medium. During the research, vibration measurements were carried out on the casing of a vapour microturbine. They aimed at monitoring the machine operation so as to detect any dynamic problems (e.g. defects or malfunction). The measurement results in the form of RMS vibration velocity levels were presented and discussed. (C) 2017 Elsevier Ltd. All rights reserved.