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Generators, transformers and UPS systems are rated in kVA, while most devices are rated in kW. The power factor connects them. Enter one value and the power factor to get the other.

Enter your values

Pick what you know and what you want to find.
From the rating plate of the generator, transformer or UPS.
Where do I find this?

kVA (kilovolt-amperes) is on the rating plate. 1 kVA = 1000 VA.

If you only know volts and amps: kVA = V × A ÷ 1000 (× 1.73 for three-phase).

Between 0.1 and 1. Often 0.8 on generators; 1 for heaters.
Where do I find this?

The power factor is on the rating plate (cos φ) or in the manual. Many generators are rated at 0.8.

Resistive loads such as heaters have 1. Motors and electronics are lower. If unknown, 0.8 to 0.9 is a common estimate.

Result

Enter your values to see the result.

Real power
– kW
Reactive power
– kVAR

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How it is calculated

  • Real power (kW) = apparent power (kVA) × power factor
  • Apparent power (kVA) = real power (kW) ÷ power factor
  • Reactive power (kVAR) = √(kVA² − kW²)

Example

A 10 kVA generator with power factor 0.8 can supply 10 × 0.8 = 8 kW. To run an 8 kW load at power factor 0.8 you need 8 ÷ 0.8 = 10 kVA.

What this estimate leaves out

The power factor of a real load changes with its operation. Size generators and UPS systems with a margin, and have an electrician check the choice.

Written and reviewed by QLines, Cologne · Last reviewed

FAQ

Frequently Asked Questions

How do you convert kVA to kW?

Multiply the kVA by the power factor: kW = kVA × power factor. A 10 kVA generator at power factor 0.8 supplies 8 kW.

How do you convert kW to kVA?

Divide the kW by the power factor: kVA = kW ÷ power factor. 8 kW at power factor 0.8 needs 10 kVA.

What is power factor?

It is the ratio of real power (kW) to apparent power (kVA), a number between 0 and 1. A value of 1 means all the current does useful work.

What is kVAR?

kVAR is reactive power, the part of the apparent power that does no useful work but still loads the cables and the generator.

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