This article discusses the design features of plants operating on the principle of organic Rankine cycle. Firstly, the choice of organic Rankine cycle as the most effective technology for utilization of low-potential heat by comparison and analysis with other technologies is justified. Secondly, the technique of selection and calculation of the installations working on the principle of an organic Rankine cycle, taking into account features of a choice of a working body, type of the expander, and also a configuration is offered. Third, an example of the calculation of the prototype of such a 4 kW unit operating on the thermal energy of hot water from the boiler, the simulation of which is performed in the program SmoWeb, the results of which it was designed. Fourth, the design for this technology takes