Non-intrusive appliance load monitoring

Definition
Non-intrusive appliance load monitoring (NALM) is a process for analyzing changes in the voltage and current going into a house and deducing what appliances are used in the house as well as their individual energy consumption.

Overview
Electric meters with NALM technology are used by utility companies to survey the specific uses of electric power in different homes. NALM is considered a low cost alternative to attaching individual monitors on each appliance. It does, however, present privacy concerns.

Privacy concerns
NALM can detect what types of appliances people have and their behavioral patterns. Patterns of energy use may indicate behavior patterns, such as routine times that nobody is at home, or embarrassing or illegal behavior of residents, without the homeowner knowing that they are being monitored. It could, for example, reveal when the occupants of a house are using the shower, or when individual lights are turned on and off.