A passive, non-contact piezoelectric microelectromechanical system sensor, aimed to perform monitoring of electricity consumption in DC electrical appliances with current switching, was proposed and demonstrated. A micro-magnet was integrated into the proposed sensor and an appropriate position for locating the micro-magnet was theoretically determined. A prototype piezoelectric sensor was fabricated, and an impulse piezoelectric voltage output was detected from a two-wire electrical appliance cord without using cord separator and driving power when switching a DC electric current on or off. A linear relationship between the measured peak value of the impulse output voltage and the applied DC electric current was obtained. The difference between the measured value and the calculated one was further theoretically considered from the view point of impedance effect.