Convert apparent power to real power
| Load Type | PF |
|---|---|
| Resistive | 1.0 |
| Computer PSU | 0.6-0.7 |
| Motors | 0.8-0.9 |
| LED lights | 0.9+ |
VA (volt-amperes) is apparent power, while watts is real power. The difference is due to reactive power in AC circuits. To convert, multiply by the power factor.
Watts = VA × Power Factor. A 1000VA UPS with PF 0.7 can deliver 700W of real power.
UPS systems are rated in VA, but your equipment consumes watts. Understanding this conversion helps you properly size backup power systems.
Multiply VA by power factor: Watts = VA × PF. For resistive loads, PF=1. For computers, use PF 0.6-0.7. For motors, use PF 0.8-0.9.
Depends on power factor. At PF 1.0: 1000W. At PF 0.8: 800W. At PF 0.6: 600W. Most UPS manufacturers assume PF 0.6-0.7 for computer loads.
Power factor (PF) is the ratio of real power to apparent power, ranging from 0 to 1. It indicates how efficiently electrical power is being used. Low PF means more current is needed for the same real power.
Only for purely resistive loads like heaters and incandescent bulbs. For reactive loads (motors, computers, fluorescent lights), watts is always less than VA.