What Is the kVA to kW Conversion and How Is It Calculated?
Kilovolt-amperes (kVA) measure apparent power, the total power a source must supply, while kilowatts (kW) measure real power that does useful work. Converting between them requires the power factor (PF), a number between 0 and 1 describing how efficiently current is converted into work.
The kVA to kW formula, derived from the AC power triangle, is: kW = kVA × PF. To go the other way, kVA = kW ÷ PF. Here kW is real power, kVA is apparent power, and PF is the cosine of the phase angle between voltage and current. Reactive power follows from kVAR = √(kVA² − kW²).
To find line current, use I = kVA × 1000 ÷ V for single-phase systems and I = kVA × 1000 ÷ (√3 × V) for three-phase systems, where V is the line-to-line voltage in volts.
According to the International Electrotechnical Commission (IEC) convention used on most generator nameplates, standby generators are rated at a power factor of 0.8, so a 100 kVA generator delivers 80 kW of real power.
How to Use This kVA to kW Calculator
Choose a direction, enter your values, and the results update instantly:
- kVA → kW or kW → kVA: Pick the conversion direction, then enter the known power.
- Power Factor: Between 0 and 1. Use 0.8 for generators, 0.9 for typical UPS units, and 1.0 for resistive loads such as heaters.
- Phase and Voltage (optional): Select single or three-phase and enter the line voltage to get current in amps.
The kW and kVA conversion is identical on 50 Hz and 60 Hz systems. Only the voltage differs by region: 230 V single-phase and 400/415 V three-phase are common in the UK, Europe and Australia, while North America uses 120/240 V single-phase and 208, 480 or 600 V three-phase.
kVA to kW Conversion Table
The table shows the real power in kW for common kVA ratings at typical power factors.
| kVA | kW at PF 0.8 | kW at PF 0.9 | kW at PF 1.0 |
|---|---|---|---|
| 10 kVA | 8 kW | 9 kW | 10 kW |
| 25 kVA | 20 kW | 22.5 kW | 25 kW |
| 50 kVA | 40 kW | 45 kW | 50 kW |
| 100 kVA | 80 kW | 90 kW | 100 kW |
| 500 kVA | 400 kW | 450 kW | 500 kW |
Frequently Asked Questions
How do you convert kVA to kW?
Multiply kVA by the power factor: kW = kVA × PF. For example, a 100 kVA load with a power factor of 0.8 delivers 100 × 0.8 = 80 kW of real power.
How many kW is 1 kVA?
One kVA equals 0.8 kW at a power factor of 0.8, 0.9 kW at 0.9, and exactly 1 kW at a power factor of 1.0. The result depends entirely on the power factor of the load.
What is the difference between kW and kVA?
kW is real power that performs useful work, while kVA is apparent power, the vector sum of real and reactive power. kVA is always equal to or greater than kW, and equipment such as generators and transformers is rated in kVA.
What power factor should I use if I do not know it?
Use 0.8 for generators and mixed industrial loads, 0.9 for modern UPS systems, and 1.0 for purely resistive loads such as heaters. Check the equipment nameplate or a power meter for an exact value.