# kVA or kW: what's the difference?

> kW and kVA explained simply: active power, apparent power and cos φ. Why generators and grid connections are rated in kVA.

Source: https://www.darkside-energy.com/en/did-you-know/kva-vs-kw/ · Dark Side Energy · Updated: 2026-10-12

12 October 2026 · 2 min read

- The kW measures active power, the power your equipment actually consumes.
- The kVA measures apparent power: it determines the size of cables, protection devices and sources.
- The two are linked by cos φ: active power = apparent power × cos φ.

You have listed your equipment: everything is in kW. You ask for a generator, and the answer comes back in kVA. Is it the same thing? Not quite, and the difference matters.

## Back to basics

The [kW and the kVA](https://www.darkside-energy.com/en/glossary/#kva-kw) do not measure the same thing.

The **kW** (kilowatt) measures **active power**: the power the equipment actually consumes to produce light, sound, heat or movement.

The **kVA** (kilovolt-ampere) measures **apparent power**: voltage multiplied by current. In single-phase, S = U × I; in three-phase, S = √3 × U × I. At a given voltage, it is what sets the current in the cables: so it determines the size of cables, protection devices and sources.

Between the two sits [cos φ](https://www.darkside-energy.com/en/glossary/#cos-phi), the power factor: active power = apparent power × cos φ. For a purely resistive load, it equals 1 and kW equal kVA. For motors or some electronic power supplies, it is lower than 1: you then need more kVA than kW.

For example, 22 kW in three-phase 400 V with a cos φ of 0.9 require 22 ÷ 0.9, or about 24.4 kVA. The current is then 22,000 W ÷ (√3 × 400 V × 0.9), or about 35.3 A per phase. With a cos φ of 1, the same 22 kW would need only 22 kVA, or about 31.8 A per phase. The conversion formulas are in our [FAQ](https://www.darkside-energy.com/en/faq/#kw-en-amperes).

That is why generators, battery packs and grid connections are rated in kVA: a source must deliver all the current drawn, whatever the cos φ of the equipment plugged into it. The kVA tell you what it can supply; the cos φ of your equipment tells you how many kW you will get from it.

## To sum up

To know what your equipment consumes, look at the kW. To choose cables, protection devices and the source, think in kVA. And if you do not know the cos φ, our calculator assumes 0.9 by default, an assumption you can change.

> kW is what you consume. kVA is what you need to plan for.

Convert your kW into kVA and amps, in single-phase or three-phase.

[Open the electrical calculator](https://www.darkside-energy.com/en/electrical-calculator/#conversion)

[What is the diversity factor?](https://www.darkside-energy.com/en/did-you-know/diversity-factor/)

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