Thermal capacity of building envelope has an effect of reducing heating and cooling storage load. This paper argues how much peak and cumulative energy can be reduced by utilizing building thermal storage. The author has already proposed a dynamic optimization technique solving such a problem. In this paper, the optimization technique is employed for annual calculation where the object system is an office room equipped with electric-driven packaged air conditioner. The optimized functions are 1) cumulative electricity, 2) peak electricity, and 3) electricity charge. Electricity charge optimization is dealt with as multi-objective problem composed of minimizing cumulative electricity and minimizing peak electricity. The optimal trajectory of room air temperature and electrical demand are also investigated for each season.