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Apparent Power Converter
Convert between volt-amps, kilovolt-amps and megavolt-amps.
A generator rated at 10 kVA cannot necessarily run 10 kW of equipment, and the gap between those two numbers has stranded more than one job site with a machine that trips out under a load that, on paper, looked well within budget.
Apparent power is not the same thing as real power
Apparent power, measured in volt-amps (VA), is simply voltage multiplied by current. Real power, measured in watts (W), is the power actually doing useful work — turning a motor, lighting a bulb, running a compressor. The two are equal only for a perfectly resistive load like an old-style heater.
For anything with a motor, transformer or switching power supply, current and voltage drift out of phase with each other, and apparent power ends up larger than real power. The ratio between them is the power factor, and it is the number generator suppliers, electricians and utility companies all quietly care about.
The three figures on a nameplate
- Apparent power (VA / kVA) — voltage × current, with no allowance for phase difference. This is what a generator or UPS is rated in.
- Real power (W / kW) — the power that actually gets converted into work, heat or light. This is what appears on your electricity bill.
- Power factor — real power divided by apparent power, a number between 0 and 1. A power factor of 0.8 means 20% of the apparent power is not doing useful work.
Unit conversions
| From | To | Multiply by |
|---|---|---|
| VA | kVA | 0.001 |
| kVA | VA | 1,000 |
| kVA | MVA | 0.001 |
| MVA | kVA | 1,000,000 VA equivalent |
| kVA × power factor | kW | use actual PF, typically 0.8–0.95 |
Where this actually matters
- Sizing a generator or UPS: manufacturers rate them in VA or kVA, but your equipment’s power draw is usually listed in watts, so you need the power factor to size correctly.
- Data centres: UPS capacity is quoted in kVA, and undersizing against real power factor is a common cause of an unexpected shutdown under peak load.
- Utility billing: industrial customers with poor power factor are often charged a penalty, because the utility still has to generate and deliver the full apparent power.
- Motor starting: an induction motor’s power factor can dip sharply at startup, briefly pulling far more apparent power than its running rating suggests.
Apparent power questions
What is the difference between kVA and kW?
kVA is apparent power — voltage multiplied by current with no adjustment for phase. kW is real power, the portion actually doing work. They are equal only when the power factor is exactly 1, which almost never happens with real electrical loads.
How do I convert kVA to kW?
Multiply the kVA figure by the power factor. A 10 kVA generator running a load with a 0.8 power factor delivers 8 kW of real power, not 10. Always check the equipment’s actual power factor rather than assuming 1.
Why do generators get rated in kVA instead of kW?
Because the generator’s windings and insulation are limited by current and voltage, not by how much of that power ends up doing useful work. Rating in kVA describes the machine’s physical limit regardless of what you plug into it.
What is a typical power factor for household equipment?
Simple resistive loads like incandescent bulbs and heaters sit close to 1.0. Motors, fridges, air conditioners and fluorescent or LED drivers with unfiltered supplies typically run 0.7 to 0.95, which is why real-world kW draw is usually noticeably lower than the kVA rating suggests.
Can apparent power ever be lower than real power?
No. Apparent power is always equal to or greater than real power, because the power factor cannot exceed 1. If you see a real power figure larger than the apparent power figure for the same load, one of the numbers is wrong.
