What’s up with VA ratings anyway?

A volt-amp (VA) is basically just another unit for measuring power. Like the watt (W), it describes a quantity of electrical power used, supplied, or otherwise handled by an electrical or electronic device.

In choosing a particular UPS for your purpose, you will need to know your system’s total power draw in either watts or volt-amps, or you may need to convert some values to one or the other unit. As VA seems to be the unit of choice for manufacturers of UPS units, it would be easiest to convert all your equipment ratings to this standard and add them up to get your total power requirement. Calculating 50% to 100% more than this is a good idea to allow for future expansion of your system without having to worry about your UPS not meeting your power requirements.

To convert from W to VA, multiply by 1.4, or to go the other way, multiply by 0.714. Your total VA rating of all your equipment (minus things like laser printers and scanners that don’t really need battery backup) must not exceed the rating of the UPS you purchase. If so, you may simply end up tripping circuit breakers or blowing fuses inside the UPS (which require warranty repair personnel to replace). Not to mention that loading a UPS fully, even though it is supposed to be designed for it, will shorten its useable life due to excessive heat buildup inside the unit.