Investigating knowledge, perceptions as well as attitudes of the public that concern various aspects of environmental issues is of high importance for Environmental Education. An integrated understanding of these parameters can properly support the planning of Environmental Education curriculum and relevant educational materials. In this survey we investigated knowledge and attitudes of secondary school teachers in Greece towards renewable energy sources, particularly wind and solar energy systems. A questionnaire with both open and closed questions was used as the main methodological instrument. Findings revealed that although teachers were informed about renewable energy sources and well disposed towards these sources, they hardly expressed clear positions regarding several issues about wind and solar energy technologies and farms. Moreover such themes are limited integrated in teaching either as extra curricular educational programs or through the curriculum. These findings cannot confirm that teachers could influence students' opinions towards renewable energy systems. Thus, authorities should invest more in Environmental Education and relevant Teachers' Education.