Summary
This white paper helps explain the differences between watts and VA and explains how the terms are
correctly and incorrectly used in specifying power protection equipment.
Introduction
This note helps explain the differences between watts and VA and explains how the terms are correctly and incorrectly used in specifying power protection equipment. Many people are confused about the distinction between the watt (W) and volt-amp (VA) measures for UPS load sizing. Many manufacturers of UPS and load equipment add to this confusion by failing to distinguish between these measures.
The power drawn by computing equipment is expressed in watts or volt-amps (VA). The power in watts is the real power drawn by the equipment. Volt-amps are called the "apparent power" and are the product of the voltage applied to the equipment times the current drawn by the equipment. Both watt and VA ratings have a use and purpose. The watt rating determines the actual power purchased from the utility company and the heat loading generated by...