Volt-amps (VA) to Kilowatts (kW) Conversion Calculator

What this tells you

A generator or UPS rated in VA can only deliver its full apparent power into a perfectly resistive load. Connect anything with motors or electronic supplies and some of that capacity goes to reactive current that does no work. This conversion tells you how many kilowatts of real, usable power a VA rating actually yields at a given power factor — the headroom question for equipment that was sized in apparent-power terms.

The VA to kW formula

is apparent power, is the power factor from 0 to 1, and dividing by 1,000 rescales watts to kilowatts. Multiplying by the power factor removes the reactive part; the division just changes units.

Worked example

The calculator’s defaults are 5,000 VA at a power factor of 0.8.

Apply the power factor:

Rescale to kilowatts:

So a 5,000 VA source delivers 4 kW of real power into an 0.8-power-factor load. The reactive component is VAR — carried by the wiring, absent from the energy meter.

VA to kW by power factor

VA, kVA and MVA

The same conversion works at any scale; only the prefix changes. 1 kVA is 1,000 VA and 1 MVA is 1,000 kVA, or 1,000,000 VA. Utility transformers and large generators are rated in MVA, so for those:

A 2.5 MVA transformer feeding a load at a 0.9 power factor delivers kW of real power. Converting the other direction, from kW to VA, divides by the power factor instead; the kW to VA calculator does that step.

Don’t re-size the supply from this

The kW figure is smaller than the VA figure, but that doesn’t mean the source has spare capacity. The reactive power the calculation strips away still occupies the generator’s alternator and the feeder conductors. Size the supply against the VA rating; use this kW result only to understand how much real work that VA can do.

Common mistakes

• Assuming unity power factor for a motor or electronics load, which overstates the usable kW.
• Sizing a generator from the kW result instead of the original VA.
• Forgetting the ÷ 1,000 and reporting watts as kilowatts.

For the watt-scale version, use the VA to watts calculator. For the reverse, see kW to VA, and for line current, VA to amps.

Reading a UPS label

Many UPS units list both ratings, for example 1,500 VA / 900 W. That implies a design power factor of . The kW figure is the limit that matters for your equipment’s real power, so check both: a 1,000 W load would overload this unit even though it’s well under 1,500 VA.

The reactive part

Apparent, real and reactive power form a right triangle:

A 5 kVA load drawing 4 kW of real power has kVAR of reactive power. That reactive current flows back and forth without doing useful work, but it still heats the cables and takes up generator and transformer capacity.

Why power factor matters on a bill

Some commercial tariffs charge for low power factor or for peak kVA demand. Raising the power factor with capacitor banks reduces the kVA drawn for the same kW, which can lower those charges and free up capacity on the supply.