Larger UPS systems are rated in V-A
Thursday, August 13th, 2009The confusion is unique to the small (under 1000 VA) UPS market due to the fact
that all UPS systems above this power level (from 1kVA to 500kVA) are rated in V-A
rather than Watts. The use of the Watt rating for small UPS systems appears to
stem from the simple marketing fact that the typical small UPS user is much
more familiar with the concept of the Watt rating. 
Nevertheless, the V-A rating system is better for matching the load to the UPS. This is true because the fundamental factor that limits the output capacity of a UPS is its output CURRENT capability, which is more closely related to the V-A rating than the Watt rating.