A system and method are provided for calculating power using a voltage waveform shape measurement from a contactless sensor. An electrically conductive medium carries alternating current (AC) electrical current, associated with an AC voltage, from a source node to a destination node. AC current is measured through the electrically conductive medium. Using a contactless sensor, an AC voltage waveform shape is measured. The power usage at the destination node is calculated in response to the AC current measurement, the measurement of the AC voltage waveform shape, and an AC voltage potential. For simplicity, the AC current and AC voltage waveform shape may both be measured at a first node located between the source node and the destination node. The AC voltage potential used in the power usage calculation may be an estimate, an actual measurement, or a value supplied by an external source (e.g., the power utility).