We conducted several tests with this power supply, as described in the article Hardware Secrets Power Supply Test Methodology.

First we tested this power supply with five different load patterns, trying to pull around 20%, 40%, 60%, 80%, and 100% of its labeled maximum capacity (actual percentage used listed under “% Max Load”), watching how the reviewed unit behaved under each load. In the table below we list the load patterns we used and the results for each load.

If you add all the power listed for each test, you may find a different value than what is posted under “Total” below. Since each output can vary slightly (e.g., the +5 V output working at 5.10 V), the actual total amount of power being delivered is slightly different than the calculated value. On the “Total” row we are using the real amount of power being delivered, as measured by our load tester.

The +12V1 and +12V2 inputs listed below are the two +12 V independent inputs from our load tester and during all tests the +12V1 input was connected to the power supply +12V1 and +12V3 rails while the +12V2 input was connected to the power supply +12V2 rail.

Input	Test 1	Test 2	Test 3	Test 4	Test 5
+12V1	5 A (60 W)	11 A (132 W)	16 A (192 W)	22 A (264 W)	31 A (372 W)
+12V2	5 A (60 W)	10 A (120 W)	16 A (192 W)	21 A (252 W)	23 A (276 W)
+5V	2 A (10 W)	4 A (20 W)	6 A (30 W)	8 A (40 W)	10 A (50 W)
+3.3 V	2 A (6.6 W)	4 A (13.2 W)	6 A (19.8 W)	8 A (26.4 W)	10 A (33 W)
+5VSB	1 A (5 W)	1.5 A (7.5 W)	2 A (10 W)	2.5 A (12.5 W)	3 A (15 W)
-12 V	0.5 A (6 W)	0.5 A (6 W)	0.5 A (6 W)	0.5 A (6 W)	0.5 A (6 W)
Total	148.4 W	299.7 W	450.1 W	599.9 W	748.9 W
% Max Load	19.8%	40.0%	60.0%	80.0%	99.9%
Room Temp.	44.5º C	46.9º C	48.2º C	46.8º C	49.8º C
PSU Temp.	44.0º C	45.3º C	48.1º C	50.0º C	50.2º C
Voltage Stability	Pass	Pass	Pass	Pass	Pass
Ripple and Noise	Pass	Pass	Pass	Pass	Pass
AC Power	179.3 W	354.9 W	541.1 W	735.0 W	946.0 W
Efficiency	82.8%	84.4%	83.2%	81.6%	79.2%
AC Voltage	115.7 V	113.8 V	111.6 V	109.3 V	105.3 V
Power Factor	0.995	0.994	0.996	0.997	0.997
Final Result	Pass	Pass	Pass	Pass	Pass

ASUS U-75HA can really deliver its labeled power at 50º C, which is great. If you pull between 40% and 60% from this power supply labeled power (between 300 W and 450 W) you will see very good efficiency between 83% and 84%. At light load (20% load, i.e., 150 W) efficiency was of 82.8%, not bad at all. At 80% load (600 W) efficiency dropped to 81.6%, still above the 80% mark. And at full load (750 W) efficiency dropped a little bit below 80%, at 79.2%. These are definitely far better results than the ones achieved by the 500 W and by the 650 W power supplies from ASUS.

This unit is 80 Plus-certified, but you need to keep in mind that this organization tests power supplies at 23º C (a temperature that is too low in our opinion), while we tested this power supply at 50º C. The higher the temperature, the lower efficiency is.

Voltage regulation was one of the highlights from ASUS U-75HA. During tests one through four all voltages stayed within 3% from their nominal values, i.e., closer to their nominal values than required, as the ATX specification allows voltages to be up to 5% from their nominal values. This includes -12 V, an output that usually doesn’t like to stay so close to its nominal value. During test five the +3.3 V output went outside this tighter range, but was still inside the maximum allowed (5%).

Noise and ripple levels stayed low all the times. Below you can see the results for test number five, when the power supply was delivering 748.9 W. The maximum allowed is up to 120 mV for +12 V outputs and up to 50 mV for +5 V and +3.3 V outputs. All numbers are peak-to-peak.

click to enlarge
Figure 15: +12V1 input from load tester at 748.9 W (42.8 mV).

click to enlarge
Figure 16: +12V2 input from load tester at 748.9 W (47.8 mV).

click to enlarge
Figure 17: +5V rail with power supply delivering 748.9 W (18.4 mV).

click to enlarge
Figure 18: +3.3 V rail with power supply delivering 748.9 W (16.6 mV).

Let’s see if we could pull more than 750 W from the reviewed unit.