One of the keys to efficient systems based on renewable energy sources is an expander. On the one hand, it has to be reliable, efficient and erosion resistant but on the other hand, it has to be cheap so the system is economically viable. Tesla radial turbine could be a potential candidate for this purpose. In the paper, a comprehensive numerical and experimental analysis of the Tesla turbine is presented. The turbine rotor has 5 discs with 160mm in diameter and changeable inter-disc gaps within range 0.3-1.2mm. It is supplied with four converging nozzles, each providing air to all inter-disc gaps. The turbine works in the subsonic regime because the maximal pressure ratio is equal to 1.8 and the inlet temperature is equal to 298K, which results in maximal generate power on the level of 200W. Results from the experiment are compared to numerical analysis. The simulations are performed with the use of Ansys CFX commercial software, which is based on the finite volume method. Comparison of power and efficiency characteristics are in good agreement. An attempt to find the influence of different geometrical and thermodynamic parameters on power and efficiency is presented in the paper.