kW to VA Calculator

Divide the real power by the power factor, then scale to volt-amps: VA = kW x 1000 / PF. A 10 kW load at a power factor of 0.8 needs 12,500 VA (12.5 kVA) of apparent power. At a power factor of 1.0, kilowatts and kilovolt-amps are numerically equal, so a 10 kW resistive load is exactly 10,000 VA. The lower the power factor, the more VA the supply has to deliver for the same useful kW.

Use the figure on the equipment nameplate where one exists. Failing that, typical values are 0.8 to 0.9 for induction motors under load, 0.95 to 1.0 for modern IT equipment with corrected power supplies, and 1.0 for purely resistive loads such as heating elements. For a mixed commercial site, 0.85 to 0.9 is a reasonable starting assumption, but a half-hourly meter or clamp meter reading gives the real answer.

Because most AC loads draw some current that does no useful work. Motors and transformers need magnetising current, which adds reactive power on top of the real power doing the job. Apparent power (VA) is the combination of the two, so it is always equal to or greater than the real power. The power factor is the ratio between them: at PF 0.8, every 800 W of useful power requires 1,000 VA from the supply.

Only the scale: 1 kVA is 1,000 VA, exactly as 1 kW is 1,000 W. Small equipment such as desktop UPS units is usually rated in VA, while generators, transformers and electricity supplies are rated in kVA. This calculator returns VA, so divide by 1,000 to compare the result against a kVA rating on a generator nameplate or a connection agreement.

UK businesses on half-hourly supplies agree a capacity with the network operator in kVA, not kW. Your equipment is sized by the kW it consumes, but the network sees the kVA it draws. At a power factor of 0.8, a 100 kVA agreed capacity can only support 80 kW of real load, so a poor power factor effectively shrinks the supply you are paying to reserve.