In the present study the performance of two-stage gravitational water vortex turbine (GWVT) assembled in a conical basin with Savonius blade profile configuration has been investigated at different flow rate and vortex elevation. Two-stage GWVT with conical basin, not only increases the performance parameters with increase in flow parameters, but the lower stages also feed additional impact to the stage located above it because of forced vortex generation in the vicinity of top stage. Moreover, maximum hydraulic head drop near the orifice is the main contributor in the power generation of the bottom stage, by giving rise to strong tangential velocity. A stage starts power production as soon as the parabolic surface of the vortex approaches the corners of the blades even in the absence of a significant water-blade interaction. The developed analytical model qualitatively predicts the performance of the turbine minutely leading the experimental results quantitatively.