Watts to VA Converter (W to Volt-Amps)
Convert real power in watts to apparent power in VA using the load power factor. The correct way to size a UPS, generator or inverter.
Convert Watts to Volt-Amps
1.0 for heaters and incandescent lights; 0.8 is typical for motors and computers with older PSUs.
Conversion Result
1.25 kVA, the rating a UPS, generator or inverter must meet
The gap between VA and W is the power factor penalty
Step-by-Step Engineering Calculation
- 1Apparent power: (1.250 kVA)
- 2Size generators, UPS units and inverters from the VA figure, not the watt figure, whenever the load power factor is below 1.0.
Conversion Formula & Relationship
Generators, UPS units and inverters are rated in VA, but loads are labeled in watts. Dividing watts by the power factor gives the apparent power the source must actually deliver.
Standard Conversion Example
A 1,000 W motor load with a 0.8 power factor needs a source rated at least 1,250 VA. A 1,000 VA UPS would be overloaded even though the watt number looks equal.
Quick Reference Conversion Table
| Watts (W) | Volt-Amps (VA) | Common Application / Context |
|---|---|---|
| 500 W @ PF 1.0 | 500 VA | Resistive heater load |
| 500 W @ PF 0.8 | 625 VA | Typical motor / PC load |
| 1,000 W @ PF 0.8 | 1,250 VA | Size a 1500 VA UPS for headroom |
| 2,000 W @ PF 0.9 | 2,222 VA | Modern PFC power supplies |
| 5,000 W @ PF 0.8 | 6,250 VA | Workshop / well pump circuit |
Frequently Asked Questions
Why is VA always equal to or bigger than watts?
Watts count only the power that does work. VA also includes reactive power that motors and transformers circulate. The ratio between them is the power factor, which is 1.0 at best, so VA can only equal or exceed W.
What power factor should I use if I do not know it?
Use 0.8 for mixed motor and electronic loads, 0.9 or higher for modern equipment with power factor correction, and 1.0 only for purely resistive loads like heaters and incandescent lamps.