What uses more power?

[Cythx]

Say setup A has a stock i7 950 and a GTX 570, and uses a 900w PSU with 90% efficiency rating.

and setup B has a stock i7 950 and a GTX 570, but uses a 1500w PSU with the same 90% efficiency rating.

Under the exact same conditions, doing the exact same things, the only difference being the PSU wattage

Which uses more power?

 

[Surveyor]

Efficiency varies according to power usage.

Both PSU's would draw the same amount of power if using the same components.

If the power draw was, for example, 500W then it depends on which is the most efficient at that load.

Setup A would be operating at a 55.6% load and setup B would be operating at 33.3% load.

PSU's are usually less efficient at low loads.

FYI both those PSU's are complete overkill for the system you've listed.

 

[Reaper 392]

if your looking to be specced a PSU for that kind of rig then go for either the antec 550W modular or the OCZ 850W 80+ gold, depending if you plan to add a second graphics card in SLI or not.

if its purely a hypothetical question then surveyor already covered it