1000VA Isn't 1000W: Power Factor and Why UPS Sizing Often Goes Wrong
A UPS rated "1000VA" and a power supply rated "1000W" sound like the same quantity — they're not. VA (apparent power) and W (real power) differ by the power factor, and many common devices have power factors well below 1.0, meaning a "1000VA" UPS often can't actually support 1000W of real load. Here's what power factor means, why UPS units are rated in VA in the first place, why "naive" sizing (treating VA and W as interchangeable) can leave far less headroom than expected, and how active PFC closes the gap in modern equipment.
Jun 15, 2026
