Energy efficiency is a top requirement in embedded system design. Understanding the complex issue of software power consumption in early design phases is of extreme importance to make the right design decisions. Power simulators offer flexibility and allow a detailed view on the sources of power consumption. In this paper we present XEEMU, a fast, cycle-accurate simulator, which aims at the most accurate modeling of the XScale architecture possible. It has been validated using measurements on real hardware and shows a high accuracy for runtime, instantaneous power, and total energy consumption estimation. The average