The concept of multisource energy harvesting (of light, kinetic, and thermal energy) using a single material has recently been proposed. Herein, the realization of this novel concept is discussed and insight into the electric field‐assisted modulation of photocurrent and pyroelectric current in a bandgap‐engineered ferroelectric KNBNNO ((K0.5Na0.5)NbO3‐2 mol% Ba(Ni0.5Nb0.5)O3−δ) is provided. Thereafter, direct current (DC) electrical modulation under the simultaneous inputs of light and thermal changes for photovoltaic and pyroelectric effects, respectively, is utilized to achieve several orders of increase in the output current density. This is attributed to a light‐assisted increase in the material's electrical conductivity and ferroelectric photovoltaic effect. The phenomena of electro–optic and thermo–electro–optic DC modulations are further used to propose two novel energy‐conversion cycles. The performance of both the proposed energy conversion cycles is compared with that of the Olsen cycle. The electro–optic and thermo–electro–optic cycles are found to harvest 7–10 times more energy than the Olsen cycle alone, respectively. Moreover, both energy‐conversion cycles offer broader flexibility and ease in operating conditions, thus paving a way toward the practical applications of multisource energy harvesting with a single material for enhanced energy‐conversion capability and device/system compactness.