You can use the above calculator to get theoretical yields for given efficiency gross head and water flow values.

The equation for net power is: P_net = e₀gpqh_gross g is the gravitational constant 9.81 and p is the water density and should be taken as 1000kg/m³ the values for the gross head :h_gross, efficiency coefficient: e₀, and water flow: q can be set related to expected local conditions.