Past decade has seen numerous data envelopment analysis (DEA)-based energy efficiency studies, which usually treat the production process as a "black box" and ignore the internal production information. This paper takes into account the joint inputs and sub-joint inputs to reveal the specific information on how inputs are allocated to outputs. To this end, we first propose an extended output-specific production technology based on which two novel energy efficiency measures are developed. We also present an empirical study on 32 countries to demonstrate the novelty and the usefulness of our method. We find that our output-specific energy efficiency measures provide a more straightforward way of dealing with undesirable output and are better capable of identifying inefficient production behavior.