Saving energy is indispensable in the solving of environmental problems such as global warming and resource depletion. In the household and office sectors, which are growing in terms of electric power consumption, it is desired to improve the efficiency of air conditioning because power consumption due to air conditioning is dominant particularly in summer when conditions of electricity usage are tight. However, the drawback with the excessive reduction in power consumption is the consequent reduction in indoor comfort levels and working efficiency. Therefore, it is important to reduce power consumption with comfort in mind. In our study, we carry out experiments on environmental measurement and control of an air conditioner by using the Keio university network oriented intelligent and versatile energy saving system (KNIVES). Three different control methods are used for evaluation of power consumption. The first method involves ON/OFF control of the air conditioner through its demand control terminal; this method is widely used. The second method involves infrared control in changing the temperature of the air conditioner by means of automatic infrared signals. The thirds method involves inverter control that changes the inverter power output of the air conditioner by using a special demand control unit. Power consumption and comfort are compared and evaluated for each of the three methods.