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Abstract The availability of materials with high electrocaloric (EC) strengths is critical to enabling EC refrigeration in practical applications. Although large EC entropy changes, ΔS_EC, and temperature changes, ΔT_EC, have been achieved in traditional thin‐film ceramics and polymer ferroelectrics, they require the application of very high electric fields and thus their EC strengths ΔS_EC/ΔEand ΔT_EC/ΔEare too low for practical applications. Here, a fundamental thermodynamic description is developed, and extraordinarily large EC strengths of a metal‐free perovskite ferroelectric [MDABCO](NH₄)I₃(MDABCO) are predicted. The predicted EC strengths: isothermal ΔS_EC/ΔEand adiabatic ΔT_EC/ΔEfor MDABCO are 18 J m kg⁻¹K⁻¹MV⁻¹and 8.06 K m MV⁻¹, respectively, more than three times the largest reported values in BaTiO₃single crystals. These predictions strongly suggest the metal‐free ferroelectric family of materials as the best candidates among existing materials for EC applications. The present work not only presents a general approach to developing thermodynamic potential energy functions for ferroelectric materials but also suggests a family of candidate materials with potentially extremely high EC performance.