Recently, with the progress in energy management system (EMS), better understanding of the detailed mechanism of energy demand occurrence becomes an important subject in energy efficiency research. One of the effective measures is the development of energy end-use simulation model. Firstly in this paper, component of energy demand formative mechanism in building sector is explained. Secondly, researches on energy end-use modeling are reviewed. In the final part, example of electricity load curve simulation in city block is introduced.