Energy efficiency is a primary concern in Wireless Sensor Networks because in general, wireless sensor nodes run on non-rechargeable batteries. Therefore, the estimating a expected node lifetime is indispensable. Thus, energy is an important issue that should be optimized by the application developer. However, in order for the developer to realize that the program may not be developed in accordance with this power restriction, it is important to estimate the energy that will be consumed by the application. In this paper we present Eprof, a cycle-accurate instruction level simulator developed to estimate the energy consumption of applications running on UNB-RISC16 processor. Eprof is able to measure detailed time-critical phenomena, and can be used to shed new light on design issues for large-scale sensor network applications.