Dietary reference values for food energy for population groups are set at the level of average energy requirement without a safety margin to avoid any risk of inadequate energy intake. Average energy requirements and hence reference values for energy can be determined from either energy intake data or energy expenditure. In this article, the present reference values for energy of 12 countries, the FAO/WHO/UNU and the Scientific Committee on Food (SCF/EC) are compared regarding the level of their standards and underlying concepts. Methods for estimating energy requirements of different population groups and data sources for reference values for energy are summarized. Furthermore, reference values for energy for males and females of all ages are presented in separate graphs. The comparison of national standards illustrates that the level of reference values for energy for individual countries is dependent on variables such as methodology, data sources, allowances for physical activity, reference body weight, and age range. Standards for adolescents and elderly persons reveal that differences in reference values are most apparent in population groups for which only limited data on energy requirements are available. Although it is not possible to evaluate the adequacy of reference values for energy by comparing data of different countries, many differences in the level of reference values can be explained on the basis of underlying concepts.