The aim of this study is to determine prospective physics teachers' level of understanding of the concepts of energy and the related concepts of force and power. The study was carried out with the participation of 56 physics education department students at a university in Karadeniz region. All participants had previously taken an introductory physics course. To reach the aim of the study, an achievement test with 5 questions was formed for each concept and the collected data was analyzed using the description method. The data analysis revealed that majority of the students were not at the intended level in defining and explaining the energy, power and force concepts scientifically, and they could not associate these concepts with their daily life. Backed by the available results, utilizing associations of these concepts and using conceptual change texts were suggested for effective teaching of the concerned concepts. (Contains 10 tables.)