The purpose of this research is to develop a teaching material for heat transfer with which students can understand energy efficiency quantitatively, and a learning task for students to investigate the utility of energy. With the teaching material, students can easily calculate heat efficiency by just measuring the heat of alcohol fuel and the change of water temperature. Moreover, the developed learning task led the students in pair to design and carry out their original experiment. The result is that 37 out of 40 pairs carried out a successful experiment and in sum 98 ways to evaluate heat energy efficiently were suggested by the pairs. Therefore, it can be considered that the material and the task effectively worked in the class.