The development of bulk piezoelectric ceramics with high energy conversion efficiency is of decisive importance for the requirements of the advanced energy harvesting devices toward miniaturization and integration. There is an additional motivation in the piezoelectric ceramics, lead titanate-zirconate (PZT) ceramics are the most widely used energy harvesting (EH) materials. This fact is important because legal restrictions on the use of lead in electronic devices have led to greater efforts being made to develop lead-free alternatives to PZT-based materials. Here, we propose the Bi0.5(Na0.8K0.2)0.5TiO3 (BNKT) lead-free piezoceramics as a good candidate for the replacement of toxic lead compounds for energy harvesting applications. For that, we have carried out a systematic study of the voltage generation of BNKT-based piezoceramics for (EH) purposes. Specifically, our results reveal that the BNKT–based lead-free piezoceramics show adequated effective capacitance and output energy due to more effective performance with a piezoelectric charge coefficient and a maximum generated output voltage as high as 12.8 pC/N and 19.9 V, respectively. Finally, we consider that the design of new lead-free piezoceramics with superior property coefficients and functionalities, such as the BNKT-based piezoceramics, should be seriously considered as candidates for the replacement of the current toxic lead-based compounds.