Efficiency, Temperature And Noise
Efficiency
Our efficiency testing procedure is detailed here.
Using the results from the previous page, we plotted a chart showing the ERX750AWT's efficiency at low loads, and loads from 10 to 110 percent of its maximum-rated capacity.
Under normal loads, the ERX750AWT is highly efficient and passes the high-end Corsair RM750i/x units, losing only to EVGA's 750 GQ. Efficiency isn't as good under light loads though, showing that this platform is tuned with normal loads in mind.
Efficiency At Low Loads
In the following tests, we measure the efficiency of the ERX750AWT at loads significantly lower than 10 percent of its maximum capacity (the lowest load the 80 PLUS standard measures). The loads we dialed were 20, 40, 60 and 80W. This is important for representing when a PC is idle, with power-saving features turned on.
| Test # | 12V | 5V | 3.3V | 5VSB | DC/AC (Watts) | Efficiency | Fan Speed (RPM) | Fan Noise | PF/AC Volts |
|---|---|---|---|---|---|---|---|---|---|
| 1 | 1.206A | 0.491A | 0.469A | 0.195A | 19.64 | 60.36% | 805 | 30.1 dB(A) | 0.894 |
| 12.073V | 5.085V | 3.400V | 5.086V | 32.54 | 115.1V | ||||
| 2 | 2.441A | 0.979A | 0.970A | 0.391A | 39.73 | 78.18% | 805 | 30.1 dB(A) | 0.938 |
| 12.078V | 5.080V | 3.394V | 5.078V | 50.82 | 115.1V | ||||
| 3 | 3.674A | 1.465A | 1.475A | 5.070A | 59.78 | 83.24% | 805 | 30.1 dB(A) | 0.960 |
| 12.074V | 5.075V | 3.388V | 5.070V | 71.82 | 115.1V | ||||
| 4 | 4.903A | 1.974A | 1.949A | 0.787A | 79.78 | 86.08% | 805 | 30.1 dB(A) | 0.970 |
| 12.072V | 5.071V | 3.383V | 5.065V | 92.68 | 115.1V |
At very light loads (<40W), this PSU isn't particularly efficient. Only during the last two tests does the ERX750AWT pass 80 percent. The fan rotates at its lowest speed during those benchmarks, generating very little noise.
5VSB Efficiency
The ATX specification states that 5VSB standby supply efficiency should be as high as possible, recommending 50 percent or higher efficiency with 100mA of load, 60 percent or higher with 250mA of load and 70 percent or higher with 1A or more of load.
We take four measurements: one each at 100, 250 and 1000mA, and one with the full load the 5VSB rail can handle.
| Test # | 5VSB | DC/AC (Watts) | Efficiency | PF/AC Volts |
|---|---|---|---|---|
| 1 | 0.102A | 0.52 | 67.53% | 0.074 |
| 5.088V | 0.77 | 115.1V | ||
| 2 | 0.252A | 1.28 | 74.85% | 0.153 |
| 5.085V | 1.71 | 115.1V | ||
| 3 | 1.002A | 5.08 | 76.28% | 0.367 |
| 5.067V | 6.66 | 115.1V | ||
| 4 | 2.502A | 12.60 | 74.25% | 0.472 |
| 5.035V | 16.97 | 115.1V |
The 5VSB rail is very inefficient, which is a shame in a Gold-rated PSU.
Power Consumption In Idle And Standby
In the table below, you'll find the power consumption and voltage values of all rails (except -12V) when the PSU is idle (powered on, but without any load on its rails), and the power consumption when it's in standby mode (without any load, at 5VSB).
| Mode | 12V | 5V | 3.3V | 5VSB | Watts | PF/AC Volts |
|---|---|---|---|---|---|---|
| Idle | 12.190V | 5.090V | 3.407V | 5.091V | 9.10 | 0.553 |
| 115.1V | ||||||
| Standby | 0.12 | 0.012 | ||||
| 115.1V |
Phantom power is low enough, though that doesn't seem to improve the 5VSB rail's efficiency.
Fan RPM, Delta Temperature And Output Noise
Our mixed noise testing is described in detail here.
The first chart below illustrates the cooling fan's speed (in RPM), and the delta between input and output temperature. The results were obtained at 36 °C (96.8 °F) to 47 °C (116.6 °F) ambient temperature.
The next chart shows the cooling fan's speed (again, in RPM) and output noise. We measured acoustics from one meter away, inside a small, custom-made anechoic chamber with internals completely covered in sound-proofing material (be quiet! Noise Absorber kit). Background noise inside the chamber was below 18 dB(A) during testing, and the results were obtained with the PSU operating at 36 °C (96.8 °F) to 47 °C (116.6 °F) ambient temperature.
The following graph illustrates the fan's output noise over the PSU's operating range. The same conditions of the above graph apply to our measurements, though the ambient temperature was between at 28 °C (82.4 °F) to 30 °C (86 °F).
The fan's noise is kept close to 30 dB(A) for most of the ERX750AWT's operating range and under normal thermal conditions. This makes it an especially quiet unit that won't bother anyone with a sensitivity to fan noise.
