The performance of self-excited induction generator was thoroughly analyzed regarding the value of the critical excitation capacitance and the frequency of the generated voltage. Analytical expressions were derived for the value of the minimum excitation capacitor under different load types/operating conditions. The advised expressions were verified experimentally and by, a robust meta-heuristic optimization technique, Genetic Algorithm. Furthermore, the feasibility, suitability and effectiveness of the proposed formulas were corroborated for generators with different sizes/ratings through the correlation of the results from the derived expressions and Genetic Algorithm for such machines.