The load difference between peaks and valleys of daily electricity demand in large cities exceeds 50% of the peak load. This causes problems with the need for high investment costs of power plants but with low running efficiencies during valley periods. Further, the large electricity load difference has caused a lot of renewable energy to be insufficiently utilized so that the curtailment of wind power and photo voltaic (PV) power occurs occasionally. The fluctuation of electricity consumption in buildings is the main cause of the electricity load difference. In order to solve these problems, this paper proposes a novel solution that utilizes a direct current power supply and distributed electricity storage in buildings to achieve a constant electricity demand from the grid. The problem of daily electricity load difference can be solved and the utilization of wind power and PV power can be promoted. In order to check the feasibility of the proposed system, a Simulink model was built to study the key issues of DC power supply and distributed power storage in buildings. The simulation model included AC/DC converters, DC/DC converters, batteries, wiring network, and electricity loads of three ordinary office rooms. The control objective of the proposed system was to maintain constant electricity use from the power grid by charging batteries during off-peak periods and discharging them during peak periods for the purpose of shifting the building peak power demand from the grid. Simulation results show that the objective of maintaining constant electricity use from the grid can be achieved with high accuracy using the proposed DC power supply and distributed battery system.