An endoreversible Carnot cycle is presented in this paper for a heat engine using high-temperature waste heat. The endoreversible Carnot cycle is a modified Carnot cycle, where the heat transferred between the heat engine and its surroundings is the only irreversible process. Since the energy input (waste heat) to the heat engine is free, the cost of the output power of the heat engine depends mainly on the size of the heat exchangers. A specific power, power per unit area of heat exchanger surface area, is adopted as the objective function for the performance analysis of the heat engine. The relation between the maximum obtainable specific power and the temperature range in which the high-temperature waste heat engine operates is found.