I. Introduction
Non-intrusive load monitoring, also known as energy disaggregation, was first introduced by Gorge W. Hart in 1980s [1]. By nature it is a single-channel blind source separation (BSS) problem that aims to decompose the aggregated power readings of a household into appliance-wise power consumption. One of the major purposes of NILM is to reduce energy consumption efficiently and pursue the green home vision. Evidences have shown that the itemized information could encourage householders to use energy in a more sustainable way, achieving about 15% energy saving [2], [3]. Besides, NILM can be leveraged to evaluate conservation programs, improve the quality of load forecasting, and provide references for power grid management [4]. For example, with real-time NILM, utility companies could suggest switching operations on particular appliances (e.g., air conditioners) for load shifting in peak power hours [3].