Thermal efficiencies were calculated based on an ideal shape-memory-effect heat-engine cycle. It was found that the addition of copper in the NiTi shape-memory alloy provides an important increase of the thermal efficiency with the highest temperature transformation range. Thermal efficiency values obtained range from 4.7 to 5.3% and Carnot efficiencies were around 25%. These efficiencies have been evaluated by means of calorimetric techniques and mechanical tests for five NiTiCu shape-memory alloys.