The energy concept has been described as a difficult to learn subject in the literature. The main purpose of this study is to reveal the students' conceptions and learning difficulties about this concept. For this aim, an achievement test consisting of 5 open-ended questions were prepared. This test was administered to 36 freshmen after a preliminary pilot study. The descriptive analysis of the collected data showed that the participants could not provide a general or interdisciplinary meaning for energy concept that they could not shift easily from one representation of energy concept to another. This study also showed that students were not able to use theoretical knowledge they were supposed to have about the energy concept while explaining a casual situation in real life. Finally, the results of this study showed that learning difficulties reported decades ago in the literature still endured and that difficulties detected in secondary education level survive through higher education.