Purpose <p>This paper aims to investigate the nonlinear stochastic response of a piezoelectric energy harvesting system that incorporates time-delayed feedback, a fractional-order current-voltage relationship, and a fractional-power restoring force. Both mono-stable and bi-stable configurations are considered to assess the influence of key parameters on energy harvesting performance.</p> Methods <p>Firstly, an equivalent stochastic system is derived for the mono-stable case, and the stochastic averaging method is employed to obtain the stationary probability density function of the voltage amplitude. Then, the theoretical results are validated by Monte Carlo simulations. Finally, the proposed model is extended to the bi-stable system, where the effects of noise intensity and feedback delay are systematically examined.</p> Results <p>Time-delayed feedback induces periodic modulation of energy harvesting performance, with optimal energy conversion achieved at specific delay values. In the bi-stable system, increasing noise intensity not only enhances energy harvesting but also triggers a transition from intra-well oscillations to inter-well hopping. Moreover, an increase in feedback delay stimulates stochastic P-bifurcation while simultaneously raising the output voltage, demonstrating that delay can serve as an effective tuning parameter for performance enhancement.</p> Conclusion <p>These findings contribute to the understanding of nonlinear stochastic dynamics in systems with time-delayed feedback and fractional-order characteristics. They offer potential design strategies for improving energy conversion efficiency in advanced electromechanical devices and self-powered microsystems.</p>