In conclusion we have shown that under proper conditions nonlinear oscillators can beat the standard linear oscillators with significant increase in the harvesting efficency.It is worth noticing that the improvement obtained in moving from the linear to the nonlinear dynamics is qualitatively independent from the details of the dynamics, here represented by the analytic form of the bistable potential under consideration[4]. Moreover the dynamical features discussed here are not limited to the sole piezoelectric energy conversion but can be applied also to other principles, e.g. capacitive and inductive.They can be applied also to micro and nanomechanical resonators[5] where noise driven dynamics are considered as a promising option