Introduction: Although there are many alternative approaches in related literature to teach energy effectively, students are still hard to learn it. Also, teachers are hard to teach it. Thus, it is believed that effectiveness of new approaches should also be researched. The objective of this paper is to investigate students' understandings about energy concept in a learning environment designed in terms of 'Model Based Instruction'. For this purpose, Model of Model Based Instruction (MOMBI) as one of the model of Model Based Instruction Approach was accepted as the teaching model for the study. Method: Didactical engineering was used as the research method owing to its potential to carry out experimental study. The sample consisted of 33 students enrolled in an introductory physics course in Karadeniz Technical University in Turkey. To emerge students' understandings, the data was collected with pre and post tests including open-ended questions. The obtained data analyzed through the rubric developed in terms of related literature. Analyzes were realized by first author of the study and checked its correctness by the second author. The effectiveness of the learning environment was determined with comparing the pre and post tests results. Results: In the study, analyzes of student answers put forth three main points about students' understandings related with energy. These are energy as a concept, energy types, and relationship between energy and a system/object. The analysis of pre-test showed that the students did not try to define energy or explain it truely. It is also noticed that students did not have adaequate understandings about energy types and relationship between energy and a system/object before the instruction process. Hereby, it was determined that the students came inadequate and incorrent acquisitions to university. The analysis of post-test revealed that the students defined energy, its types and relationship of it with a system sufficiently. Thus, it was decided that the students' understandings increased at the expected quality after the instruction process. Moving from here, the study was concluded that the learning environment designed in terms of MOMBI had an effective nature to teach energy subject.Suggestions: Based on the results, MOMBI was recommended to lecturer or teachers in the instruction processes. Also, since Model Based Instruction Approach and its MOMBI model was highlighted in recent years, it is recommended to researchers to carry out new researches on this field.