In what unit is transformer power capacity rated?

Transformer power capacity is rated in kilovolt-amperes (kVA). This unit reflects the apparent power, which considers both the voltage and current carried by the transformer without taking into account the power factor. The use of kVA as the unit of measure is crucial because transformers can supply power in both resistive (real) and reactive (imaginary) forms, making kVA a more comprehensive indicator of the transformer's capacity to handle electrical loads.

While watts (W) could be used for measuring real power, it does not capture the total power that a transformer can manage, especially in scenarios involving inductive loads where power factor becomes significant. Kilowatt-hours (kWh) represents energy consumed over time and is not appropriate for capacity rating. Amperes (A) measure current but do not encompass the voltage aspect necessary for determining a transformer's overall capacity. Therefore, kilovolt-amperes stands out as the correct unit for expressing a transformer's power capacity.