A home network comprising: n electric devices (21 to 30) disposed in a house, where n is 2 or a larger integer; n modules (11 to 20, 11A to 20A) being provided corresponding to the n electric devices (21 to 30), each supplying power to the corresponding electric devices from an outlet and detecting power usage states of the corresponding electric devices; detection means detecting operational states of actually operating m electric devices based on n power usage states transmitted from the n modules (11 to 20, 11A to 20A), where m is an integer that satisfies 2 ≤ m ≤ n; and characterized in that the n modules (11 to 20, 11A to 20A) are adapted to detect disposed positions of the corresponding electric devices; the detection means are adapted to detect a positional relation between the m electric devices based on the n disposed positions transmitted from the n modules (11 to 20, 11A to 20A); the home network further comprises estimation means (6, 6A) estimating the number of residents in the house by determining achievability of operational states of the m electric devices based on the detected positional relation and operational states of the m electric devices, the estimation means (6, 6A) being adapted to output the number of residents to at least one of the following: sensing means adapted to sense an intruder in the house; and warning means adapted to warn the residents of sensing of an intruder; wherein the home network further comprises: the sensing means sensing an intruder in the house by determining achievability of operational states of the m electric devices with respect to the estimated number of residents and the detected positional relation and operational states of the m electric devices; and the warning means warning the residents of sensing of an intruder if the sensing means senses the intruder. n electric devices (21 to 30) disposed in a house, where n is 2 or a larger integer; n modules (11 to 20, 11A to 20A) being provided corresponding to the n electric devices (21 to 30), each supplying power to the corresponding electric devices from an outlet and detecting power usage states of the corresponding electric devices; detection means detecting operational states of actually operating m electric devices based on n power usage states transmitted from the n modules (11 to 20, 11A to 20A), where m is an integer that satisfies 2 ≤ m ≤ n; and characterized in that the n modules (11 to 20, 11A to 20A) are adapted to detect disposed positions of the corresponding electric devices; the detection means are adapted to detect a positional relation between the m electric devices based on the n disposed positions transmitted from the n modules (11 to 20, 11A to 20A); the home network further comprises estimation means (6, 6A) estimating the number of residents in the house by determining achievability of operational states of the m electric devices based on the detected positional relation and operational states of the m electric devices, the estimation means (6, 6A) being adapted to output the number of residents to at least one of the following: sensing means adapted to sense an intruder in the house; and warning means adapted to warn the residents of sensing of an intruder; the n modules (11 to 20, 11A to 20A) are adapted to detect disposed positions of the corresponding electric devices; the detection means are adapted to detect a positional relation between the m electric devices based on the n disposed positions transmitted from the n modules (11 to 20, 11A to 20A); the home network further comprises estimation means (6, 6A) estimating the number of residents in the house by determining achievability of operational states of the m electric devices based on the detected positional relation and operational states of the m electric devices, the estimation means (6, 6A) being adapted to output the number of residents to at least one of the following: sensing means adapted to sense an intruder in the house; and warning means adapted to warn the residents of sensing of an intruder; sensing means adapted to sense an intruder in the house; and warning means adapted to warn the residents of sensing of an intruder; the sensing means sensing an intruder in the house by determining achievability of operational states of the m electric devices with respect to the estimated number of residents and the detected positional relation and operational states of the m electric devices; and the warning means warning the residents of sensing of an intruder if the sensing means senses the intruder.