kVA Explained
Contact UsWhat Does kVA Mean in Diesel Generators?
If you're comparing generator sizes, you've probably seen ratings in kVA. Understanding what kVA means — and how it differs from kW — is essential for choosing the right diesel generator.
What is kVA?
kVA stands for kilovolt-amperes. It represents the apparent power of a generator — the total power available before accounting for efficiency losses caused by electrical loads.
Most diesel generators in the UK are rated in kVA rather than kW because generators supply both:
- Real Power (kW) – The usable power that performs work.
- Reactive Power (kVAr) – Power required by inductive loads like motors.
kVA vs kW – What’s the Difference?
The relationship between kVA and kW depends on something called the power factor (PF).
Formula:
kW = kVA × Power Factor
In the UK, most generators are rated at a standard 0.8 power factor.
| Generator Size (kVA) | Power Factor | Usable Power (kW) |
|---|---|---|
| 100 kVA | 0.8 | 80 kW |
| 200 kVA | 0.8 | 160 kW |
| 500 kVA | 0.8 | 400 kW |
Why Power Factor Matters
Power factor reflects how efficiently electrical power is used. Equipment like motors, compressors and pumps reduce power factor, meaning more kVA is required to deliver the same kW output.
This is why correct generator sizing is critical — especially on industrial and agricultural sites.
Prime vs Standby kVA Ratings
- Standby Rating: Used during mains failure only. No overload capability.
- Prime Rating: Designed for continuous use with limited overload allowance.
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