We proposed an integrated system for utilizing hydrogen energy in commercial buildings. This system consists of a fuel cell device, a water electrolysis device, metal hydride tanks and their auxiliary devices. This system contains elements that contribute to electrical power load leveling and providing a stable supply of power during emergencies. By making actual use of this system, we were able to make simultaneous and effective use of electricity, hydrogen, and heat. This paper presents an evaluation that assesses the energy efficiency of this system by calculation. Results from evaluating the possibility of future use of hydrogen systems in commercial buildings in terms of total energy efficiency allowed reaching the following conclusions. (1) The higher the building heat-electricity rate and the higher the waste heat utilization rate, the more superior the hydrogen system is to other systems. The hydrogen system may prove a crucial system for attaining efficient energy utilization, especially in terms of heat management. (2) Compared to ice storage, the hydrogen system attains at least a 27% energy savings for the entire building. Due to efficient energy usage, the hydrogen system is highly likely to be installed in office buildings in the future. We demonstrated that the hydrogen system is the most effective in terms of effective energy use compared with ice storage systems and co-generation systems.