About

In Alternating Current (AC) systems, not all energy delivered to the device is used to do useful work. The Apparent Power (S), measured in Volt-Amperes, is the total power flow. The Real Power (P), measured in Watts, is the power actually consumed. The ratio between them is the Power Factor (PF).

Ignoring Power Factor is a primary cause of UPS failure and generator overloading. For example, a computer server rated at 1000 VA with a PF of 0.7 only draws 700 W of real power. This tool accurately converts these values.

Formulas

The formula connects Apparent Power vectorially to Real Power.

P_(W) = S_(VA) × PF

Power Factor (PF) is a dimensionless number between 0 and 1.

Reference Data

Device Type	Typical Power Factor (PF)	Efficiency Note
Incandescent Light / Heater	1.0	Resistive Load (Pure conversion)
Standard Electric Motor	0.80 - 0.90	Inductive Load
Personal Computer / Server	0.65 - 0.75	Switch Mode Power Supply
LED Lighting	0.90 - 0.95	Driver dependent
UPS System (Input)	0.99	Active PFC correction
Welding Equipment	0.50 - 0.70	Highly Inductive

Frequently Asked Questions

If you assume PF is 1.0 for inductive loads (like motors or computers), you will overestimate the Wattage capacity required, which is safe but expensive. However, if converting Watts to VA (reverse) with PF=1, you will undersize your cables/generator, causing breakers to trip.

It is often listed on the device nameplate or technical datasheet. If not listed, 0.8 is a safe industry standard estimate for mixed loads.

UPS components (inverters/wiring) are limited by the total current (Amps) flowing through them, which correlates to VA, not just the Watts doing the work.

No. Real Power (Watts) is a component of Apparent Power (VA). Mathematically, PF cannot exceed 1.0, so Watts ≤ VA.