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kVA is a unit of apparent power, a measure used in electrical engineering. It stands for kilovolt-ampere. Apparent power is the product of the root-mean-square (RMS) voltage and RMS current in an AC circuit. It is represented by the symbol S and is measured in volt-amperes (VA) or kilovolt-amperes (kVA).

While power in a DC circuit is simply voltage multiplied by current (P = V x I), in an AC circuit, the situation is more complex due to the presence of reactive components like inductors and capacitors. These components store and release energy, causing the current and voltage waveforms to be out of phase. Apparent power accounts for both the real power (which does useful work) and the reactive power (which is associated with energy storage and release). The relationship between them is described by the power triangle, where apparent power is the hypotenuse, real power is one leg, and reactive power is the other.

kVA is commonly used to rate the capacity of electrical equipment such as transformers, generators, and uninterruptible power supplies (UPS). This is because the physical size and heat dissipation of such equipment are often more closely related to the apparent power they can handle rather than just the real power. For example, a transformer's rating in kVA indicates the maximum volt-amperes it can safely supply without overheating. When specifying electrical loads or capacities, kVA provides a convenient and practical measure of overall electrical demand.