Equal channel angular pressing (ECAP) was conducted at room temperature to impose high strain into high purity copper. Differential Scanning Calorimeter (DSC) was used to estimate the stored energy from ECAP and recrystallization temperature. It was found that the stored energy increases upon ECAP processing until a peak is reached at 12 passes of ECAP, and a slight decrease in stored energy was observed at higher ECAP passes. The recrystallization temperature decreases upon the increase of the stored energy up to similar to 50 J/mol, and reaches a stable valve of similar to 210 A degrees C. Partial annealing of an ECAP processed (8 passes) sample by heating to similar to 185 A degrees C at a heating rate of 20 A degrees C/min released the stored energy from similar to 55 to similar to 18 J/mol, without substantial change on the recrystallization temperature of the sample. A two parameters model was used to help calculate stored energy of ultrafine-grained copper after high strain level processing.