A generator or inverter is rated in kVA — apparent power. But the load it actually drives is measured in kW — real power. The two are not the same, and the gap between them is set by the power factor. The conversion is simply kW = kVA × power factor. It's one of the first sums you do when matching a generator to a load.
A worked example
Take a 10 kVA generator rated at the usual 0.8 power factor. Its real output is 10 × 0.8 = 8 kW. The reactive part is 10 × sin(arccos 0.8) = 6 kVAR. Notice the neat 3-4-5 shape: 8 kW, 6 kVAR, and 10 kVA form a right triangle, because kVA² = kW² + kVAR². That triangle is the whole story of apparent, real, and reactive power in one picture.
Why it matters
If you size a generator by its kVA number and ignore the power factor, you'll overestimate how much real load it can carry. A 10 kVA set won't run 10 kW of equipment — only 8 kW at a 0.8 power factor. For purely resistive loads like heaters, the power factor is close to 1, so kVA and kW nearly match; for motors it's lower, so the shortfall is bigger.
Related tools
Match the source to the load with the generator sizing calculator and the inverter calculator. To go from power to current for wiring, use the watts to amps calculator, and for energy over time see the kWh to kW calculator.
Frequently asked questions
How do you convert kVA to kW?
Multiply kVA by the power factor: kW = kVA × PF. For example, 10 kVA at 0.8 is 8 kW. To reverse it, divide: kVA = kW ÷ PF.
What is a typical power factor?
Generators are usually rated at 0.8. Resistive loads like heaters sit near 1.0; motors and mixed loads fall between 0.7 and 0.85.
What is the difference between kVA and kW?
kVA is apparent power the source must supply; kW is the real power that does work. The power factor links them, and the difference shows up as reactive power in kVAR.