Abstract

The transition to renewable energy is hindered by the level of acceptance in society. The role of education in schools is crucial, and while numerous studies have been conducted, there is still a lack of exploration into the depth of the materials. This research was carried out to assess the readability level of material on renewable energy from geothermal resources in Vocational High School textbooks. The descriptive quantitative method was used, conducted in 19 Vocational High School with a study program in Technology and Engineering in Surakarta. The sample size was 340 respondents. Data were collected from textbooks and questionnaire results. The Gunning Fog Index scores indicated the material had low readability level with scores of 20, 18, and 21 for texts 1, 2, and 3. Text 1 is taken from book titled 'Energy Conversion Machines', Text 2 from 'Sustainable Energy Saving through Building', and Text 3 from 'Basic Knowledge of Mechanical Engineering. Additionally, the responses of readers indicated that more than 50% of respondents could easily comprehend the content in texts 2 and 3. Resulting, for text 1, over 50% of respondents reported understanding the content with some difficulty. These three books are also commonly used, making this research a valuable recommendation for stakeholders in curriculum design and educational planning.