A smart tap into which one or more power plugs can be inserted, comprising: a voltage waveform measurement unit, a current waveform measurement unit, a communication unit, a control unit, and an arithmetic unit, wherein the voltage waveform measurement unit and the current waveform measurement unit are adapted to measure a voltage waveform and a current waveform, respectively, of power supplied to each of one or more home appliances via a corresponding one of respective power plugs connected to the home appliances, and wherein the communication unit is adapted to transmit the voltage waveform and the current waveform or a result of processing of the waveforms to a server which is installed in a place separate from the smart tap and further adapted to receive a control signal based on a result of computation in the server, and wherein the control unit is adapted to control switching of the power supplied to the home appliance and the amount of the supplied power in accordance with the control signal, characterized in that the control unit is further adapted to control the amount of the power supplied to each of the home appliances with the power plugs connected to the smart tap on the basis of data on the amount of suppliable power received from the server, and wherein the smart tap further comprises a sensing unit adapted to analyze the waveforms obtained from the voltage waveform measurement unit and the current waveform measurement unit and to recognize a status of and senses an abnormality in each home appliance, and a sensing and communication unit adapted to transmit a sensing result from a sensor which is installed in a building to the server. a voltage waveform measurement unit, a current waveform measurement unit, a communication unit, a control unit, and an arithmetic unit, wherein the voltage waveform measurement unit and the current waveform measurement unit are adapted to measure a voltage waveform and a current waveform, respectively, of power supplied to each of one or more home appliances via a corresponding one of respective power plugs connected to the home appliances, and wherein the communication unit is adapted to transmit the voltage waveform and the current waveform or a result of processing of the waveforms to a server which is installed in a place separate from the smart tap and further adapted to receive a control signal based on a result of computation in the server, and wherein the control unit is adapted to control switching of the power supplied to the home appliance and the amount of the supplied power in accordance with the control signal, characterized in that the control unit is further adapted to control the amount of the power supplied to each of the home appliances with the power plugs connected to the smart tap on the basis of data on the amount of suppliable power received from the server, and wherein the smart tap further comprises a sensing unit adapted to analyze the waveforms obtained from the voltage waveform measurement unit and the current waveform measurement unit and to recognize a status of and senses an abnormality in each home appliance, and a sensing and communication unit adapted to transmit a sensing result from a sensor which is installed in a building to the server.