Our load tests utilize a couple of FAST ATE active load testers and a variety of other equipment such as an oscilloscope, power conditioner, temperature probe and a power consumption meter. You can read more about our standard testing approach here.
The tests performed are based around six conceivable setups that are out there and progressively load down the PSU up to the power supply's limits or 1000W, whichever comes first. Since our test equipment's limits are lower than that of the XFX ProSeries 1000W, we will only be able to test it to 1000W.
Let's start by taking a look at the voltages to see how well this unit did during testing. Starting with the 12V rail, we see 2% regulation from start to finish with a total drop of .25V throughout all the tests. The 5V rail didn't quite fair as well with 3% voltage regulation and a total drop of .18V. Moving towards the 3.3V rail, we see that regulation stays at 3% with a total voltage drop of .10V. This was an improvement all the way around from the 1000W model.
DC output quality was also marginally better from start to finish. Starting out, we measured noise at a low 11mV peak to peak. This steadily increased as the loads also increased. By the time we had reached around 50% load, the unit ripple had crept up to 37mV. Under Test 6 load, we saw that the noise on the 12V rail had crept up to 49mV. It would have been nice to see how much noise we were able to find under full load, but unfortunately our test equipment will not allow for higher loads.
The XFX ProSeries 1250W is rated for 80Plus Gold efficiency. This means that the power supply must perform at 97%/90%/87% efficiency at 20%/50%/100% loads respectively. As you can see, the XFX ProSeries 1250 managed to score a pass while on our test bench. Things were a little close right from the start, but quickly improved. There is no reason to suspect that the unit would have failed if we would have been able to fully load down the unit.
Overall, the XFX ProSeries 1250W power supply does very well in our testing. The unit has several improvements over what we saw with the 1000W unit. Voltage regulation is better and manages to keep everything within 3% of specification. DC output quality is better up to the 1000W mark too, but we can't say whether or not is better overall since we cannot test the unit to the full 1250W. The efficiency is right where it should be per the 80Plus Gold certification as well.
This unit also comes in at a steep price of $269.99, but when you start to factor in what you are getting, it becomes much more of a bargain. For only $20 more than the 1000W, you are getting an extra 250W of power and the capability to run an extra GPU. On top of that, you are getting marginally better performance with a minor drop in efficiency. Overall, it becomes a no-brainer that the better buy is the 1250W ProSeries unit for a number of reasons, unless the extra $20 really breaks the bank for you.