Which of the following is NOT a unit used in measuring electric power?

The choice that is NOT a unit used in measuring electric power is Hertz (Hz). Hertz measures frequency, specifically the number of cycles per second of an alternating current or a signal. In the context of electric power, it's essential to differentiate between units of power and units of frequency.

The Watt (W) is the standard unit of power, representing the rate at which energy is transferred or converted, and is commonly used for measuring electrical power. The Voltampere (VA) is another unit of apparent power in an electrical circuit, especially in alternating current scenarios, while Var (Reactive power) is used to measure reactive power in the system. Thus, while Watts, Voltamperes, and Vars all pertain directly to types of power in electrical systems, Hertz does not relate to power but rather to the frequency aspect of electric signals.