Background: Renewable energy curriculum reflects research, standards, and policy documents that emphasize both environmental literacy and engineering, technology, and science concepts. Students' science achievement in this and other areas have been found to be predicted by their teachers' content knowledge. Therefore, this study examined whether, and where, gaps in the content knowledge of pre-service teachers would be found when designing instruction on renewable energy technology for middle grades classrooms. Purpose: The purpose of this study was to explore pre-service middle grades teachers' content knowledge for the design of instruction on renewable energy technology. Design and methods: Thirteen pre-service science teachers in the final semester of a licensure program focused on grades 6-8 (ages 11-14) in the semester just prior to their student teaching experience participated. Structural coding was used to develop categories of instances of content knowledge in four artifacts related to their instructional design that was further analyzed and described. Results: The content knowledge that was used by the pre-service, middle grades science teachers when designing renewable energy technology instruction fell within three content categories inclusive of six issues with knowledge areas. Conclusions: The implications of this investigation are related to the training of middle grades science teachers and the potential necessity to explicitly support content knowledge instruction that aligns with calls for changes to how the conservation of energy is taught before student teaching. In addition, better integration of content knowledge with methods and curriculum courses are called for. The participants had satisfactory performance on both licensure exams and in required coursework. However, they had not achieved understanding of content necessary for instruction on renewable energy technology that is included in middle grades standards.