The article considers the actual task of improving the design and effectiveness of low-pressure micro-hydro units on the basis of hydraulic laboratory studies. The methodology of micro-HPS testing on an experimental stand with a rotor diameter of 350 mm in the laboratory department RESH is developed. The performance and universal characteristic of micro-HPS with impeller PL984-35 are obtained. Based on the results of experimental study the changes to the structure of micro-HPS for improving efficiency are proposed.