Herbert, In a DC circuit, you are correct, Wattage and VoltAmps are the same. But with AC you must also account for any phase shift which reduces the effective wattage. The AC formula for power is P = V * I * cosign(theta). (or something very similar.... it's been a long time since I fooled with AC circuit analysis <grin>). In a pure theoretical circuit, theta is -90 degrees which has a cosign of 1 But in actuality, the phase shift results in a cosign of less than one. Jim Meagher ===== Micro Solutions Consulting Member of The HTML Writers Guild http://www.ezy.net/~microsol International Webmasters Association 410-543-8996 MS Site Builder Network - Level 2 member ===== ----- Original Message ----- From: Herbert Graf <[log in to unmask]> > I have a question about W and VA. I just purchased a UPS (Uninterruptible > Power Supply) that has a rating of 400VA and 250W, my question is why are > they not the same? PCBUILD mailing list is brought to you by: The NOSPIN Group http://nospin.com