The objective of this research work is to investigate the effect of multiwall carbon nanotube (MWCNT) content (0.3–1.2 wt%) on a potassium sodium niobate (KNN)-based piezoelectric unimorph harvester for enhancing the energy generation capacity. KNN–MWCNT composites were fabricated by using a microwave solid state technique. The energy-harvesting performance of the KNN–MWCNT composite was determined by the base excitation method and sized to resonate between 20 and 100 Hz at 1 MΩ load resistance. The energy performance of the KNN composite at percolation threshold (0.6 wt% MWCNT) showed a maximum power generation of 2.94 μW, the power density of 7.15 μWm⁻₃ and overall efficiency of 83.75% at an input acceleration of 0.5 g and a load resistance of 1 MΩ. Improvements observed in the power generation by percolation phenomena and ionic flow over the nanotube surface of KNN composites prove to be a boon for low-power sensing devices.