What does 4000 VA mean?

j-d wrote:
This thread is interesting but it gave me a headache. Still, I take away the following:

VA doesn't mean something with rated wattage will run on advertised/rated VA.

VA is advertised instead of the more useful Wattage spec because VA is a bigger number and bigger sells better.

I'll buy a bigger UPS than I thought I needed.

If GOD wanted me messing with Electrons, HE'd've made them big enough to see.

Wattage (actual power) is never higher than VA (apparent power).

Generators and transformers and so forth are rated in VA because they are limited by the apparent power they can supply, not the actual power. In other words, a generator can only supply so much current at its specified voltage, regardless of whether the current is in phase with the voltage or not. Similarly, wires and circuit breakers or fuses must be sized for the actual current, and hence based on apparent power rather than actual power.

Advertising is in watts because that's what more people are familiar with, I guess. In the case of the UPS you described, the larger VA number simply means that it's capable of producing its full rated (actual) power for a load with a poor power factor. That is indeed an improvement over one that can only do when powering something with a nice power factor.