This study examined the impact of a practice-based approach to in-service science teacher education, using small-group discussions about photovoltaic (PV) science to support teachers' instruction on sustainable energy transitions in response to climate change risks. Ultimately, we aimed to promote teachers' PV science comprehension as well as their ability to use small-group discussions productively in their future classrooms. In-service teachers (N = 6) participated in a five-week summer Solar Energy Engineering Research Experience for Teachers program where they read a series of scientific articles, attended presentations, and engaged in small-group Quality Talk discussions, all about solar energy as a sustainable technology for post-carbon energy futures. Using a qualitative content analysis approach, we gathered evidence associated with both the indicators of high-level comprehension evidenced within the talk as well as teachers' individual PV science knowledge before and after each discussion. We also collected data related to teachers' instructional intentions via lesson plans and their self-reported future use of classroom discussions. Numerous indicators of high-level comprehension were present within the talk and teachers evidenced growth in their PV science knowledge from pretest to posttest. Additionally, teachers not only infused their lesson plans with the PV science topics they discussed, but they also expressed intentions to teach PV science using discussions in their future classrooms. Findings suggest in-service teachers can benefit from opportunities to engage in a practice-based approach emphasizing discussions, resulting in not only enhanced PV science comprehension but also intentions to enact discussions about the learned content in their future classrooms.