400 VA is the rating for a purely resistive load. 250W is it is
reactive load rating. Most UPS's are rated for a maximum power
factor of 0.8. So in other words, if you were to plug in a electric
heater it could handle 400 Watt units. The power supply in your
computer causes a reactive load and the UPS is just rated for 250
Watts in that case.


>         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? I always thought that in most circumstances P = V x I,
> and doesn't VA just mean V x I, the same thing? I have a feeling that I am
> missing something huge here. Thanks for any info.
>


Dale Laluk / [log in to unmask]
P.O. Box 308
Hudson's Hope, B.C. V0C 1V0
250-783-9921

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