User talk:66.182.113.122

Your example "a (large) UPS system rated to deliver 400,000 volt-amperes at 220 volts can deliver a current of 1818 amperes" is useless because anyone could replace the "volt-amperes" with "Watts" and it would still be true. Instead, tell us when and how "wattage" formulas give the wrong answer. Tell us why we need to understand the difference, the relevance, when someone is dealing with alternating current instead of direct current.