Some of the major hydropower plants calculations are turbine type selection, speed and diameter of runner, dimensions of draft tube and spiral case. Since manufacturers have their own professional softwares, educator and consultant engineers have to use commercial softwares or mathematical methods and rely on their results for estimation and preliminary studies.

This paper introduces result reliability of a commercial software that has special equations to calculate turbine, draft tube and spiral case, analyzing and comparing results with the mathematical method and actual values of six hydropower plants known as Maroon, Abbaspour II, Dez, Masjid Suleiman, Karkheh and Karun III located in Khuzestan Province, Iran. Comparing results of software and mathematical average errors with actual values indicated that only 6 parameters in software method and 4 parameters in mathematical method among 14 parameters have reliable results in Francis Turbine. These parameters are Runaway Speed, Runner Diameter, Shaft Diameter, A, D (spiral case parameters) and σ (Thoma number) in software method and B, C, E (spiral case parameters) and σ in mathematical method. Therefore it’s not possible to confirm all parameters calculated with mathematical or software methods in Francis turbine.