Why kVA Cannot Be Converted to kWh Directly
You cannot convert kVA directly into kWh without knowing the circuit's Power Factor (PF). Kilovolt-Amperes (kVA) measure apparent power — the total electrical capacity flowing through wires and alternators. Kilowatt-hours (kWh) measure real, usable energy consumed over time.
In any alternating current (AC) system with inductive equipment (electric motors, air conditioners, compressors, transformer windings), current and voltage fall slightly out of sync. This lag creates "reactive power" (measured in kVAR). The power factor represents the ratio of usable real power to total apparent power:
Real-World Generator Example (10 kVA Generator)
Most backup diesel and petrol generators are sold with a rating in kVA and a standard nameplate power factor of 0.8. If you run a 10 kVA generator for 6 hours:
That 10 kVA machine produces 48 kWh of usable energy. If you assumed a 1:1 conversion (ignoring power factor), you would have mistakenly budgeted for 60 kWh — an overestimation of 25% that could cause your generator to stall or trip under load.
kVA to Real kW and Hourly kWh Lookup Table
| Generator Rating (kVA) | Power Factor | Real Power (kW) | Energy (kWh / 4 hrs) | Typical Load Served |
|---|---|---|---|---|
| 2.5 kVA | 0.8 | 2.0 kW | 8.0 kWh | Small inverter, fans, refrigerator |
| 5.0 kVA | 0.8 | 4.0 kW | 16.0 kWh | 1 Ton AC + household lighting |
| 7.5 kVA | 0.8 | 6.0 kW | 24.0 kWh | 1.5 Ton AC + water pump |
| 10.0 kVA | 0.8 | 8.0 kW | 32.0 kWh | Whole house essential load |
| 15.0 kVA | 0.8 | 12.0 kW | 48.0 kWh | Multiple ACs + heavy machinery |
Frequently Asked Questions
What is the difference between kVA and kW?
kVA is apparent power (total power supplied through the system), while kW is real active power (the portion that actually does physical work). Power factor connects them: kW = kVA × PF.
What power factor should I use for my generator?
Standard diesel and gas generators are rated at a 0.8 power factor unless the manufacturer's nameplate explicitly specifies unity (1.0).
How many kW is a 10 kVA generator?
At the standard 0.8 power factor, a 10 kVA generator delivers exactly 8.0 kW of real continuous power (10 × 0.8 = 8.0 kW).
Why don't generators output their full kVA rating as usable kW?
Because inductive electrical loads like compressors and motors require magnetic fields to operate. This generates reactive power (kVAR) that occupies generator capacity without performing mechanical work.
How do I convert kVA to kWh?
First convert kVA to kW by multiplying by power factor: kW = kVA × PF. Then multiply by operational hours: kWh = kW × hours.
