kVA to kW Calculator

Direction

Value

Power factor

Result

Real power, kW8
Apparent power, kVA10
Reactive, kVAr6
Current at 220 V, A45.45
Current at 380 V, A15.19
Power factor used0.8

The difference between what is drawn and what works

Links apparent and real power through the power factor and shows the resulting current at both 220 and 380 volts.

Generators, UPS units and transformers are rated in kilovolt-amps while appliances are rated in kilowatts. They are not the same thing: kVA is the total power the equipment must pass, kW is the portion that does work.

The power factor sets the gap. A 10 kVA generator at a 0.8 power factor delivers only 8 kW of useful output — which is exactly why you cannot size one directly from the wattage of your appliances.

What this calculator shows

Real and apparent power side by side
The reactive component in kVAr
The current that power produces at 220 and at 380 volts

What to keep in mind

Take the power factor from the equipment nameplate; domestic generators are almost always rated at 0.8.
Reactive power comes from Pythagoras on apparent and real power — the standard power triangle.

FAQs

What is the difference between kVA and kW?

kVA is apparent power, voltage times current. kW is real power, the part that becomes heat, light or motion. The ratio between them is the power factor.

What power factor should I assume?

One for purely resistive heating, 0.85 for a mixed domestic load, 0.8 for anything with motors. Generator makers almost always quote 0.8.

Why are UPS units rated in volt-amps?

Because what limits them is total current through the switching stage, not useful output. A 1,000 VA unit at a 0.6 power factor will only carry 600 watts of load.

What is reactive power?

Energy shuttled back and forth between the supply and coils or capacitors without doing work. It still heats cables and loads the transformer, which is why industrial users are billed for it.

Worked example

A domestic generator

Input: 10 kVA at a 0.8 power factor

Output: 8 kW real, 6 kVAr reactive

Note: The current at 220 volts is 45 A. That figure, not the 8 kW, is what the incoming cable and breaker must be sized for.

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kVA to kW Calculator

Result

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