Energy quality refers to the characteristics of an electric power system that determine the suitability of the power for its intended use. It encompasses both the voltage and current waveform, frequency, and power factor.

A high-quality power supply has a consistent voltage, stable frequency, and a power factor close to 1.0. This means that the voltage is at the correct level, the frequency does not vary much, and the current and voltage are in phase. This type of power supply is essential for sensitive equipment such as computers and medical devices.