KVA Calculator

Kilovolt-amperes, abbreviated kVA, measure apparent power in an alternating-current circuit. Apparent power combines the voltage and current delivered by a source without assuming that they peak at the same time. For a single-phase load, apparent power in kVA equals RMS voltage times RMS current divided by one thousand. The value describes the total electrical capacity that conductors, transformers, generators, switches, and protection equipment may need to carry. Kilowatts measure real power, the portion converted into useful work, heat, light, or motion. Real power equals apparent power multiplied by power factor. Power factor ranges from zero to one and describes how effectively current contributes to useful energy transfer. A resistive heater can approach unity power factor, while motors, transformers, and electronic loads may draw current that is shifted or distorted. A 10 kVA load at 0.8 power factor therefore uses 8 kW of real power. Reactive power, expressed in kVAR, represents energy exchanged with magnetic and electric fields. For the simplified power triangle used here, reactive power equals apparent power multiplied by the square root of one minus power factor squared. Real power, reactive power, and apparent power form a right triangle: kVA squared equals kW squared plus kVAR squared. This relationship is appropriate when a single aggregate power factor accurately represents the load. Use RMS voltage and current measured under the same operating condition. This calculator is specifically configured for single-phase power. Three-phase balanced systems require an additional square-root-of-three factor when line-to-line voltage and line current are used. Also distinguish kVA from kW when sizing equipment: a generator or transformer rating is often limited by apparent power and current even when the connected load consumes fewer kilowatts. The calculated values support preliminary sizing, classroom analysis, and quick field checks. Final electrical designs must also consider startup current, harmonics, duty cycle, ambient conditions, code requirements, conductor ampacity, protective devices, and manufacturer ratings.