Currently, electricity generation requires both fossil energy resources and the supply of renewable energy. In addition, efficient energy management is necessary. This need became more pronounced in Japan after the Great East Japan Earthquake of March 2011. Since then, Japan's power supply has been limited because of the shutdown of nuclear power plants, and this has led to several problems. To deal with this problem, the effective use of renewable energies such as photovoltaic and wind power is required. Since these energy sources are unstable, batteries need to be introduced in the power grid for power supply leveling. However, the financial burden of introducing batteries on the demand side, such as in houses or buildings, is very high. To solve this problem, the required battery capacity needs to be reduced by controlling the air conditioners used by consumers in order to facilitate the peek-shift effect. In this study, we constructed a real-time simulation using a hardware-in-the-loop (HIL) system that can control air conditioners through power leveling with batteries. We propose two different cooperative demand control methods for comparison. These methods consider consumer comfort and the state of charge (SoC) of the batteries. The aim of this simulation was to compare three cases: no control, battery control, and control of both the air conditioner and the battery by a cooperative demand control method. This simulation showed that the cooperative control method achieves power consumption reduction and power leveling at the same time, which proves that the proposed method can reduce the battery capacity required for power leveling.