I'm setting up a new computer... And I took a peek at my power supply....
100-127V - 8A
So that's fully loaded power....
So 110V *8A = 880Watts
The supply is rated to deliver 300W max...
That's to say, fully loaded my power supply has an efficiency of 34%
Yes, fully loaded is one of the least efficient zones - but still, 34%?
I found a similar power supply (same model and power reqs/specs with a couple different connectors) that claims 70% minimum efficiency
ATX12V-G300BT (Bestec ATX-300-12EB3 Power Supply)
Any other explanation? What's your box say?