A nonintrusive appliance load monitor determines the energy consumption of individual appliances turning on and off in an electric load, based on detailed analysis of the current and voltage of the total load, as measured at the interface to the power source. The approach has been developed to simplify the collection of energy consumption data by utilities, but also has other applications. It is called nonintrusive to contrast it with previous techniques for gathering appliance load data, which require placing sensors on individual appliances, and hence an intrusion onto the energy consumer's property. An interesting aspect of this research is the interdisciplinary manner in which it combines power systems theory and communications theory-power consumption is decoded as an act of information transfer. The theory and current practice of nonintrusive appliance load monitoring is described, including goals, applications, load models, appliance signatures, algorithms, prototypes, field-test results, current research directions, and the advantages and disadvantages of this approach relative to intrusive monitoring, Because of its many advantages, we expect that nonintrusive techniques will supersede conventional intrusive techniques for a wide variety of load monitoring applications.
