Operational statuses (turn-on/turn-off, power consumption, and the like) of individual electrical apparatuses can be easily recognized by mounting a measuring device to a power supply of each apparatus.  However, there is a problem in that a burden is imposed on a user due to labor and time required for the installation thereof or a problem in that the cost of the measuring device is required. 
A method disclosed in Patent Document 1 is provided as a means for solving such a problem.  In this method, an operational status of an individual electrical apparatus is inferred using voltage and current information measured in the vicinity of a power feed inlet.  According to this method, it is possible to reduce a burden on a user and the cost, as compared to a method of mounting a power measuring device on every apparatus. 
In addition, Patent Document 2 discloses an apparatus inference device connected to a plurality of electrical apparatuses for inferring the types of electrical apparatuses and the like from power demand measurement results.  The apparatus inference device includes: a power demand fluctuation analysis unit that extracts a time fluctuation waveform having power demands of the plurality of electrical apparatuses being superimposed on each other therein and the magnitude of the amount of power demand fluctuation from the measurement results and extracts a plurality of time fluctuation waveforms constituted by only the magnitude of the amount of power demand fluctuation for each magnitude of the amount of power demand fluctuation; a period distribution analysis unit that extracts a representative period from period distribution of the time fluctuation waveforms; a database that stores features unique to intermittent operation of the plurality of electrical apparatuses; and an inference unit that infers an electrical apparatus in intermittent operation by comparing the extracted magnitude of the amount of power demand fluctuation and the representative period with the stored features unique to the intermittent operation of the electrical apparatuses.