Efficiency is a great buzzword today, but has several meanings in the UPS world. None of the definitions reflect what most people think of when they buy fuel efficient car, or energy efficient light bulb.
Definition 1 - Power Factor Efficiency
As I have said before, UPSes are sized in Volt Amps (VA). While the actual Wattage is usually a factor of that VA, depending on the UPS.
A 1000va UPSes can offer 900, 670, or even 500watts, depending on its Power Factor efficiency . Larger and even more expensive units can have the same apparent low efficiency. The $3500 SURTD5000XLT has a 70% Power Factor Efficiency, delivering 3500watts per 5000va unit. The MGE 5kva unit is really efficient in Power Factor, as it delivers 4500watts per 5000va unit. Whereas, the Symmetra PX UPS is 100% efficient, delivering 10kw per 10kva.
Bottomline, while this is the most important spec in UPSes, the lower power factor efficiency doesn't necessarily mean that a unit is wasting energy like our common sense of efficiency..
