A heat transfer system, comprising an electrocaloric material comprising: a copolymer of a monomer mixture comprising: (i) vinylidene fluoride, and (ii) an addition polymerization monomer selected from vinyl chloroformate, vinyl trifluoroacetate, vinyl acetate, vinyl benzoate, 1,1-dichloroethylene, 2-vinyl-1,3-dioxolane, n-vinylformamide, 2-vinylpyridine, 1-vinyl-2-pyrrolidinone, acrylonitrile, 1-cyanovinyl acetate, methacrylamide, acrylamide, methyl methacrylate or a monomer represented by the formula: wherein -R 1, -R 2, and -R 3 are each independently -H, -F, or -C(R 4) 3, and R 4 is H or F, and X is selected from OClO 2, OCN, OCIO, NO 2, ONO 2, NCO, NO, ONO, N 3, OCl, NCS, OF, SCN, CN, P(=O)F 2, PO, OCF 3, OCl, C 6 H2(NO 2) 3, NF 2, P(=O) 2, CH=CHC6H2(NO 2) 3, OCHO, OH, COOH, CF 3, OBr, CF 2 CF 3, CF(CF 3) 2, C 6 H 3 (NO 2) 2, SiF 3, P(=O)Cl 2, PF 2, GeF3, CH(CF 3) 2, CH=CHC 6 H 3 (NO 2) 2, NHOH, NCl 2, CHO, SnF 3, P(=O)Br 2, S(=O) 2 CH 3, -O-C -R 5, -NH-C -R 6, -C -NHR 6, cyano, or a heterocyclic group; electrodes (14, 16) disposed on opposite surfaces of the electrocaloric material;; a first thermal flow path between the electrocaloric material and a heat sink a second thermal flow path between the electrocaloric material and a heat source; and an electric power source configured to provide voltage to the electrodes (14, 16). a copolymer of a monomer mixture comprising: (i) vinylidene fluoride, and (ii) an addition polymerization monomer selected from vinyl chloroformate, vinyl trifluoroacetate, vinyl acetate, vinyl benzoate, 1,1-dichloroethylene, 2-vinyl-1,3-dioxolane, n-vinylformamide, 2-vinylpyridine, 1-vinyl-2-pyrrolidinone, acrylonitrile, 1-cyanovinyl acetate, methacrylamide, acrylamide, methyl methacrylate or a monomer represented by the formula: wherein -R 1, -R 2, and -R 3 are each independently -H, -F, or -C(R 4) 3, and R 4 is H or F, and X is selected from OClO 2, OCN, OCIO, NO 2, ONO 2, NCO, NO, ONO, N 3, OCl, NCS, OF, SCN, CN, P(=O)F 2, PO, OCF 3, OCl, C 6 H2(NO 2) 3, NF 2, P(=O) 2, CH=CHC6H2(NO 2) 3, OCHO, OH, COOH, CF 3, OBr, CF 2 CF 3, CF(CF 3) 2, C 6 H 3 (NO 2) 2, SiF 3, P(=O)Cl 2, PF 2, GeF3, CH(CF 3) 2, CH=CHC 6 H 3 (NO 2) 2, NHOH, NCl 2, CHO, SnF 3, P(=O)Br 2, S(=O) 2 CH 3, -O-C -R 5, -NH-C -R 6, -C -NHR 6, cyano, or a heterocyclic group; (i) vinylidene fluoride, and (ii) an addition polymerization monomer selected from vinyl chloroformate, vinyl trifluoroacetate, vinyl acetate, vinyl benzoate, 1,1-dichloroethylene, 2-vinyl-1,3-dioxolane, n-vinylformamide, 2-vinylpyridine, 1-vinyl-2-pyrrolidinone, acrylonitrile, 1-cyanovinyl acetate, methacrylamide, acrylamide, methyl methacrylate or a monomer represented by the formula: wherein -R 1, -R 2, and -R 3 are each independently -H, -F, or -C(R 4) 3, and R 4 is H or F, and X is selected from OClO 2, OCN, OCIO, NO 2, ONO 2, NCO, NO, ONO, N 3, OCl, NCS, OF, SCN, CN, P(=O)F 2, PO, OCF 3, OCl, C 6 H2(NO 2) 3, NF 2, P(=O) 2, CH=CHC6H2(NO 2) 3, OCHO, OH, COOH, CF 3, OBr, CF 2 CF 3, CF(CF 3) 2, C 6 H 3 (NO 2) 2, SiF 3, P(=O)Cl 2, PF 2, GeF3, CH(CF 3) 2, CH=CHC 6 H 3 (NO 2) 2, NHOH, NCl 2, CHO, SnF 3, P(=O)Br 2, S(=O) 2 CH 3, -O-C -R 5, -NH-C -R 6, -C -NHR 6, cyano, or a heterocyclic group; electrodes (14, 16) disposed on opposite surfaces of the electrocaloric material;; a first thermal flow path between the electrocaloric material and a heat sink a second thermal flow path between the electrocaloric material and a heat source; and an electric power source configured to provide voltage to the electrodes (14, 16).