After being in operation for more than 30 years, the revitalization project of six turbines started in Serbia in 2009. The aim was to increase the installed power as well as the efficiency by 10%. The installed turbines on Đerdap1 are old Kaplan turbines with adjustable blades, and the old design needed change and optimization. The target was to determine, through extensive tests of operational states, where the ratio of produced electricity and consumed water was the largest. For this purpose, IEENT (The Institute of Nikola Tesla in Belgrade) in cooperation with MFB (The Faculty of Mechanical Sciences, University of Belgrade) and TRC PRO (Technical Research Center) designed a concept of how to measure the efficiency in real-time under working conditions. To gain the highest effort and increase, the power production of the turbine and the mechanical design of the turbine blades were calculated and designed according to the latest standards.