kVA to kW Converter (and kW to kVA)
Convert between apparent power (kVA) and real power (kW) using power factor.
Calculate kVA, kW, kVAR, and power factor for AC electrical systems and UPS sizing.
The Power Triangle AC electrical systems have three types of power, forming a right triangle: Real Power (P, in kW): the actual power consumed and converted to useful work (heat, light, motion). Apparent Power (S, in kVA): the total power supplied by the source — what the utility bills for in large installations. Reactive Power (Q, in kVAR): power stored and returned by inductive and capacitive loads (motors, transformers) — does no useful work.
The Power Factor Power Factor (PF) = kW / kVA = cos(θ) Where θ is the phase angle between voltage and current. PF = 1.0 (unity): current and voltage are in phase — purely resistive load (heaters, incandescent bulbs). PF = 0.8 (common for motors): current lags voltage — more apparent power needed for the same real power. PF = 0.9+ (good): typical of modern efficient equipment and power factor corrected installations.
The Formulas kW = kVA × PF kVA = kW / PF kVAR = √(kVA² − kW²) PF = kW / kVA = cos(arctan(kVAR / kW))
Why kVA Matters Generators are rated in kVA because they provide apparent power, not just real power. A 100 kVA generator can supply 80 kW of real power at 0.80 PF. UPS (Uninterruptible Power Supply) systems are sized in kVA. A 10 kVA UPS at 0.9 PF can power 9 kW of actual equipment. Transformers are also rated in kVA because they are affected by both real and reactive components.
Power Factor Correction Poor power factor is expensive — utilities charge demand fees for low PF installations. Power factor below 0.85 often incurs surcharges from electricity providers. Capacitor banks are added to correct power factor toward unity by offsetting inductive reactive power. Modern variable frequency drives (VFDs) include built-in power factor correction.
Common Power Factors by Equipment Type Resistive loads (heaters, toasters): PF = 1.0. Incandescent lighting: PF = 1.0. Fluorescent lighting (electronic ballast): PF = 0.95–0.99. AC induction motors (unloaded): PF = 0.3–0.5. At full load: PF = 0.85–0.92. Computers and electronic equipment: PF = 0.6–0.7 (without PFC) or 0.95–0.99 (with active PFC). Welding equipment: PF = 0.35–0.60.
Generator and UPS Sizing Rule of Thumb For motors and mixed loads: add 25% margin above calculated kVA for startup surges. For critical IT infrastructure: size UPS at 150% of actual kW load at 0.9 PF. Standby generators should be sized at 100–125% of site peak demand in kVA.