This work harmonizes the experimental and theoretical study of electrocaloric effect (ECE) in (Pb${}_{0.8}$Bi${}_{0.2})$(Zr${}_{0.52}$Ti${}_{0.48})$O₃ solid solution by optimizing sintering temperature. Bi${}^{3+}$-doped PbZr${}_{0.52}$Ti${}_{0.48}$O₃ solid solutions were synthesized by the conventional solid-state reaction method. Different samples were prepared by varying the sintering temperature. X-ray diffraction study confirms the crystalline nature of all the samples. An immense value of polarization has been acquired in the optimized sample. The maximum adiabatic temperature change of order 2.53 K with electrocaloric strength of 1.26 K mm kV${}^{-1}$ has been achieved experimentally. Whereas a comparatively close value of ECE has been acquired from the theoretical calculations using a phenomenological approach. Furthermore, a large value (218 mJ cm${}^{-3})$ of thermal energy conversion has been obtained using the Olsen cycle.This work harmonizes the experimental and theoretical study of electrocaloric effect (ECE) in (Pb${}_{0.8}$Bi${}_{0.2})$(Zr${}_{0.52}$Ti${}_{0.48})$O₃ solid solution by optimizing sintering temperature. Bi${}^{3+}$-doped PbZr${}_{0.52}$Ti${}_{0.48}$O₃ solid solutions were synthesized by the conventional solid-state reaction method. Different samples were prepared by varying the sintering temperature. X-ray diffraction study confirms the crystalline nature of all the samples. An immense value of polarization has been acquired in the optimized sample. The maximum adiabatic temperature change of order 2.53 K with electrocaloric strength of 1.26 K mm kV${}^{-1}$ has been achieved experimentally. Whereas a comparatively close value of ECE has been acquired from the theoretical calculations using a phenomenological approach. Furthermore, a large value (218 mJ cm${}^{-3})$ of thermal energy conversion has been obtained using the Olsen cycle.