One of the challenges that the implementation of river or in-stream hydrokinetic technology faces is a lack of research providing tools and/or methodology for the assessment of economic potential including choice of the placement and quantity of hydrokinetic devices (HKDs). The present study proposes and applies the developed tool to estimate and compare economic benefits of placement of different kind of HKDs taking into account local restrictions. The paper describes in detail how the tool functionality and modelling results can serve as a basis for economical calculations and prognosis, under electricity market conditions. Experimental data along with in-flow measurements of the Daugava river’s different cross-sections have been used to demonstrate functionality of the proposed tool.