Skip to content NREL Buildings Research National Renewable Energy Laboratory (NREL)
Field Test Best Practices: A Resource for Practical Residential Building Science

Main menu

Watt (Power) Transducers

There are a variety of watt transducers available for residential energy monitoring. A watt transducer monitors the current, voltage, and the relative phase angle between the two in a circuit to determine true power delivered to a load. This information is reported as a direct current (DC) voltage or current signal proportional to the measured power. For residential (single phase, three-wire) circuits, the power in each of the two mains branches (black to neutral and red to neutral) must be monitored and summed to get the total power. Watt transducers can either use an external current transformer (CT) or an internal current transformer to measure current and have a input for sensing voltage.