kVA to kW Calculator
Enter apparent power (kVA) and power factor to calculate real power (kW) instantly.
How do you convert kVA to kW?
Multiply kVA by the power factor: kW = kVA × PF. A 100 kVA generator at 0.8 power factor delivers 100 × 0.8 = 80 kW of real power. Power factor is a number between 0 and 1; when it is unknown, 0.8 is a common assumption for mixed loads.
kVA to kW Conversion Table (kW = kVA × PF)
| Apparent power | PF 0.8 | PF 0.9 | PF 1.0 |
|---|---|---|---|
| 1 kVA | 0.8 kW | 0.9 kW | 1.0 kW |
| 5 kVA | 4.0 kW | 4.5 kW | 5.0 kW |
| 10 kVA | 8.0 kW | 9.0 kW | 10.0 kW |
| 25 kVA | 20.0 kW | 22.5 kW | 25.0 kW |
| 100 kVA | 80.0 kW | 90.0 kW | 100 kW |
| 500 kVA | 400 kW | 450 kW | 500 kW |
Formula
Generator & UPS Sizing: Why the Power Factor Gap Matters
When you buy a generator or UPS (uninterruptible power supply), the headline rating is almost always in kVA — apparent power. The actual usable power in kW depends on the power factor of the loads you connect. Getting this wrong in either direction is costly:
| Scenario | Generator/UPS rating | Load PF | Usable kW | Practical implication |
|---|---|---|---|---|
| Home standby generator (resistive loads: lights, heaters) | 10 kVA | 1.0 | 10.0 kW | Full rated capacity is usable — resistive loads are ideal generator loads. |
| Home standby generator (mixed loads: fridge, AC, TV) | 10 kVA | 0.8 | 8.0 kW | A 9 kW real-power load would overload this generator even though the kVA nameplate shows 10. |
| Office UPS (computer servers, switched-mode PSUs) | 3 kVA | 0.9 | 2.7 kW | Modern server PSUs have PF close to 1 thanks to active PFC, but older equipment can drag PF to 0.6–0.7, cutting available kW significantly. |
| Small industrial UPS (motor-driven loads) | 20 kVA | 0.7 | 14.0 kW | Motors have low lagging power factor at partial load. A 20 kVA UPS can only power 14 kW of real work here — undersizing by assuming kVA ≈ kW is a common and expensive mistake. |
Rule of thumb: always identify the worst-case power factor of your load mix before sizing a generator or UPS. Generator nameplate kVA × 0.8 is a widely used conservative estimate when the load PF is unknown.
Frequently Asked Questions
To convert kVA (apparent power) to kW (real power), multiply the kVA by the power factor. For example, 100 kVA at a power factor of 0.8 equals 80 kW.
The formula is: kW = kVA × PF, where kW is real power in kilowatts, kVA is apparent power in kilovolt-amps, and PF is the power factor (a number between 0 and 1).
Power factor measures how efficiently electrical power is converted into useful work. It ranges from 0 to 1. Resistive loads (heaters) have a power factor of 1; inductive loads (motors) typically range from 0.7 to 0.95.
At a power factor of 0.8, 100 kVA equals 80 kW. This is calculated as: 100 × 0.8 = 80.
Generators are rated in kVA because their alternator can only produce a fixed amount of apparent power regardless of load type. The actual usable real power (kW) depends on your load's power factor. A 10 kVA generator powering mixed household loads at a power factor of 0.8 delivers only 8 kW of real power. To check if a generator is big enough: total up the kW demand of your loads, divide by 0.8 (or your known load PF) to get the required kVA, then choose the next standard size up.