Formula
P (kW) = S (kVA) × PF
Worked example
A 100 kVA generator at the standard PF 0.8 rating point delivers P = 100 × 0.8 = 80 kW of real power.
Reference table
Effect of power factor
| Power factor | kW from a 10 kVA source |
|---|---|
| 0.7 | 7 |
| 0.8 | 8 |
| 0.85 | 8.5 |
| 0.9 | 9 |
| 0.95 | 9.5 |
| 1.0 | 10 |
Where this shows up in the real world
Reading a generator, transformer or UPS spec and want the real usable power? Multiply by PF. That '100 kVA' rental generator delivers about 80 kW to ordinary loads — knowledge that prevents the most common rental-counter disappointment in storm season, when half a town is sizing backup power in a hurry.
Common mistakes to avoid
Don't compare a generator's kVA to a competitor's kW as if they're the same number — marketing departments enjoy that confusion. And note PF cuts both ways: a data-center load with corrected PF near 0.99 extracts nearly the full kVA as kW, while an old workshop full of induction motors at 0.75 leaves a quarter of the rating on the table.
Frequently asked questions
My generator says 100 kVA — how many kW is that?
At the standard 0.8 PF rating, 80 kW. If your actual load runs at a higher PF, you may extract more kW, up to the engine's limit.
Can PF ever be exactly 1?
Purely resistive loads (heaters) reach PF ≈ 1, in which case kVA and kW are equal.
Which figure goes on my electricity bill?
Energy billing uses kWh (kW × hours). Some commercial tariffs add demand charges based on peak kW or kVA.