Abstract: A wall plug power monitor accurately measures power consumption of an appliance connected via a wall plug power monitor to AC power supplies of any of the various frequencies used around the world. A three milliohm current sense resistor minimizes power consumption caused by current sensing. Digital oversampling and filtering methods allow for accurate calculation of voltage, current, and power consumption despite line noise and a minimized current sense resistor. Voltage sampling timed to correspond to positive-voltage pulses of voltage measurement signals and current sampling independently timed to correspond to positive-voltage pulses of current measurement signals allow the wall plug power monitor to be used with AC power supplies of varied and varying frequencies. A bit reservation system that scales values to preserve least significant digits allows accuracy while using an inexpensive integer-based processor.