Abstract: To improve the energy conversion efficiency of flutter-based piezoelectric energy harvesters and avoid the inefficiency of exhaustive numerical simulations, this study establishes an electromechanical model based on Euler–Bernoulli beam theory, piezoelectric coupling and modal superposition. Closed-form expressions are derived for the cut-in wind speed, tip displacement, and harvested power. These expressions are compared with numerical results to establish the model’s accuracy and domain of applicability. The analytical results establish the proposed damping-matching criterion, which links the load resistance to the equivalent electrical damping. When the achievable electrical damping reaches its optimal value, the model simultaneously achieves a lower cut-in speed, higher power output, and reduced displacement. When the maximum attainable damping falls below the optimal level, selecting the highest achievable damping still yields near-optimal power output while effectively suppressing displacement. Furthermore, the optimal harvested power increases markedly with free-stream velocity and with aerodynamic empirical coefficients. At a wind speed of 18 m/s, an isosceles triangular bluff body with a 30° apex angle under optimal damping achieves a peak power output that is 3.71 times that of a square prism and 2.85 times that of an isosceles triangular bluff body with a 53° apex angle. These analytical damping-matching criteria and design guidelines offer efficient and practical guidance for selecting circuit parameters and designing bluff-body geometries.