Determining occupancy from a WiFi router's electric power consumption in an office environment

The goal of most modern energy management systems in buildings is to reduce unnecessary waste and cut peak electric demand. Underpinning this need is the ability to detect the number of people occupying a given space. This allows for both the ability to shut down all nonessential devices contributing to the electric waste while no one is present, as well as optimise the amount of electricity used in heating, ventilation and air conditioning, depending on the number of people present. In this paper we demonstrate that it is possible to determine the number of people in a room by monitoring the electric power consumption of a WiFi router. We show that the WiFi router's minimum power consuption can be used as features to determine the number of connected devices and link this to the types of data packets used by the network. Finally, we also perform measurements in an office environment and show that it is possible to classify the number of people with high accuracy.