A device to be connected to first electrical power wiring and for displaying electrical power usage information of at least one first electrical load connected to the first electrical power wiring, the device including terminals to electrically connect to the first electrical power wiring of a building, a controller to receive information representing at least a current to the at least one first electrical load, determine first electrical power usage information of the at least one first electrical load using the received information, a user interface to display the determined first electrical power usage information of the at least one first electrical load, and a communications interface to transmit the determined first electrical power usage information to at least one second electrical device for display, and receive determined second electrical power usage information of at least one second electrical load from the at least one second electrical device for display.

A device to be connected to first electrical power wiring and for displaying electrical power usage information of at least one first electrical load connected to the first electrical power wiring, the device including terminals to electrically connect to the first electrical power wiring of a building, a controller to receive information representing at least a current to the at least one first electrical load, determine first electrical power usage information of the at least one first electrical load using the received information, a user interface to display the determined first electrical power usage information of the at least one first electrical load, and a communications interface to transmit the determined first electrical power usage information to at least one second electrical device for display, and receive determined second electrical power usage information of at least one second electrical load from the at least one second electrical device for display.

Provided is a network system. The network system includes: at least one unit selected from an energy receiving unit receiving energy and an energy management unit managing the energy receiving unit. An energy usage amount or energy usage rate of the energy receiving unit is adjusted; an energy usage amount or usage rate when the unit is controlled based on information relating to at least an energy rate is less than that when the unit is controlled without the base of information relating to at least an energy rate; the energy receiving unit comprises a plurality of components; and an operation of one component among the plurality of components is controlled based on the energy rate related information.

A method of displaying power consumption by receiving information regarding Real Time Pricing (RTP) in which a power rate varies according to time; receiving power consumption amounts; and displaying predetermined visual displaying means based on the RTP information and the received power consumption amounts.