Sustainable development includes controversial values and complex issues such as energy consumption contra natural resources. This paper discusses a school project involving teachers from pre-schools to upper secondary schools in Sweden. The project aimed to support the teaching of energy issues and more generally sustainable development. During the first year of the project, teachers attended a university course as part-time students. The purpose of this paper is to discuss the meaning of an education for sustainable development (ESD) school project from the teacher's point of view. The research question is as follows: How do teachers constitute meaning in an ESD project? Through focus group interviews, I found three themes that illuminate the meaning of the project: awareness, confirmation, and collaboration. This study opened up two horizons: the meaning of ESD and the meaning of prerequisites for successful teaching. According to the results of this study, the relationship between social and ecological issues needs local relevance and people need an opportunity to debate the controversial issues.