Due to increasing demand for electricity, the exploit of renewable energy resources has become essential. Despite the small amount of electricity produced by small hydropower plants, have such investments many other advantages. Before starting a project of small hydro power plant, it is vital to analyze quality input data of selected location for using water potential. In assessment of hydroenergetic potential of the Reka river in Topolc, the point of old object revitalization has been determined, in which water potential has already been exploited. We start with analysis and evaluation of daily flow measurements from gauging station in Trnovo. Topographical terrain data were collected with the geodetic location recordings. The aim of such an assessment is primarly to get the annual amount of electricity produced and the viability of investment. Calculations of produced power and electricity were compared with calculations from company Siapro, which were obtained from the owner of the object Mr. Barbiš. The comparison was made for double regulated Kaplan turbine, which, given the circumstances, is not proven to be optimal choice. Economic viability has been proven by analyzing cash flow, with the results of net present value (NPV) for a statutory discount rate (DS) and internal rate of return (IRR). The obtained results are a good basis for developing a conceptual design, or for further project activities, if the owner will decide to build small hydropower plant.