kVA ↔ kW conversion
Convert apparent power to real power and back using the power factor cos φ – for generators, UPS units and transformers.
Calculate
Real power P: 80 kW
Reactive power Q: 60 kvar
How the conversion works
Real and apparent power are related by P (kW) = S (kVA) × cos φ. Generators, transformers and UPS units are rated in kVA because they are limited by current regardless of how much of it the load actually uses; consumption is billed in kW.
If you don't know the power factor, 0.8 is the usual assumption for mixed loads. The calculator also shows the reactive power Q = √(S² − P²), which flows between source and load without doing useful work.
Worked examples
| Input | Result |
|---|---|
| 100 kVA, cos φ = 0.8 | 80 kW |
| 50 kVA, cos φ = 0.9 | 45 kW |
| 10 kW, cos φ = 0.8 | 12.5 kVA |
| 230 kW, cos φ = 0.95 | ≈ 242.1 kVA |
Frequently asked questions
Why are generators and UPS units rated in kVA?
Their windings and semiconductors are limited by current, i.e. apparent power – regardless of the connected load's power factor. How many kW you actually get depends on the load's cos φ.
Which power factor should I use?
If unknown, 0.8 is the common estimate for mixed loads. Resistive loads have 1, modern PFC power supplies 0.95 – 0.99, older motors as low as 0.7.
What is reactive power?
The component of power that oscillates between source and load (motor magnetic fields, capacitors) doing no useful work. It is given in var: Q = √(S² − P²).
Can the kW value exceed the kVA value?
No. Since cos φ is at most 1, real power never exceeds apparent power – in the ideal case they are equal.
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Last updated: 16 July 2026