Depletion of resources and climate change are important factors impacting sustainable development. Energy education, as part of education for sustainable development, is considered an efficient way to raise students' awareness of environmental protection and energy saving. This study aimed at understanding the energy literacy of high school students in Vietnam, and explored the factors that influence students' energy-saving behavior as a basis for considering the effectiveness of the energy education program. An online and paper version energy-literacy survey was conducted. Participants were 600 12th-graders from high schools in Northern, Central and Southern Vietnam. Structural equation modeling was used to test the hypotheses of the relationships between energy knowledge, energy-related values, attitude toward energy saving, energy saving intention and behavior. Welch's ANOVA was conducted to examine whether energy-saving behavior differed by group. The results showed that 12th-graders' energy knowledge tended to be low, while their perceived values, attitude, intention and behavior related to saving energy were relatively high. There was no direct effect of energy knowledge on their energy-saving intention or behavior, while an indirect effect was observed if value and attitude toward energy saving were taken as mediators. Based on the participants' self-reported data, public-school students performed more behaviors to reduce energy consumption than those from private schools. In addition, the major source from which students gained energy knowledge was the mass media. According to the results, implications related to energy policy and instruction were generated.