Heats of combustion and formation of various energetic thermoplastic elastomers. (ETPE), corresponding to linear copolyurethanes based on an energetic prepolymer and a diisocyanate, were measured by a calorimetric method. These ETPEs were synthesized from three different molecular weights of glycidyl azide polymer, from poly(3-nitratomethyl-3-methyloxetane) and from poly glycidyl nitrate. The prepolymers were also analyzed for comparison with the corresponding ETPEs. A significant difference of the heats of formation was observed between the prepolymers; and their ETPEs, while the heats of combustion were similar.