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 efficiency of the Snow Silent 750 at low loads, and loads from 10 to 110 percent of the PSU's maximum-rated capacity.
With 230VAC input, this is among the most efficient 750W PSUs we have ever tested. The same applies to light-load tests. Seasonic's improved XP2S platform can be considered among the best money can buy today in this medium-capacity category.
Efficiency At Low Loads
In the following tests, we measure the efficiency of the Snow Silent 750 at loads significantly lower than 10 percent of the device's 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 | Power(DC/AC) | Efficiency | Fan Speed | Fan Noise | PF/AC Volts |
|---|---|---|---|---|---|---|---|---|---|
| 1 | 1.197A | 0.491A | 0.476A | 0.191A | 19.58W | 72.90% | 0 RPM | 0 dB(A) | 0.832 |
| 12.145V | 5.034V | 3.348V | 5.131V | 26.86W | 115.0V | ||||
| 2 | 2.426A | 0.989A | 0.985A | 0.390A | 39.74W | 82.28% | 0 RPM | 0 dB(A) | 0.927 |
| 12.145V | 5.034V | 3.348V | 5.124V | 48.30W | 114.9V | ||||
| 3 | 3.658A | 1.478A | 1.491A | 0.584A | 59.84W | 85.76% | 0 RPM | 0 dB(A) | 0.959 |
| 12.144V | 5.033V | 3.347V | 5.118V | 69.78W | 114.9V | ||||
| 4 | 4.873A | 1.983A | 1.970A | 0.780A | 79.74W | 87.83% | 0 RPM | 0 dB(A) | 0.970 |
| 12.144V | 5.034V | 3.347V | 5.111V | 90.79W | 115.0V |
The PSU's efficiency under light loads is superb in three out of the four load tests we conducted, easily surpassing the 80 percent mark. In addition, the fan didn't spin at all during these tests, allowing the unit to achieve zero noise output.
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 will take four measurements: one each at 100, 250 and 1000mA, and one with the full load the 5VSB rail can handle.
| Test # | 5VSB | Power (DC/AC) | Efficiency | PF/AC Volts |
|---|---|---|---|---|
| 1 | 0.102A | 0.52W | 73.24% | 0.095 |
| 5.136V | 0.71W | 115.5V | ||
| 2 | 0.252A | 1.29W | 76.79% | 0.197 |
| 5.131V | 1.68W | 115.5V | ||
| 3 | 1.002A | 5.13W | 78.68% | 0.394 |
| 5.116V | 6.52W | 115.5V | ||
| 4 | 3.002A | 15.23W | 80.58% | 0.490 |
| 5.073V | 18.90W | 114.9V |
Efficiency performance on the 5VSB rail was average. This surprised us, since the older Seasonic X-750 managed to significantly outperform the higher-grade Snow Silent unit.
Power Consumption In Idle And Standby
| Mode | 12 V | 5 V | 3.3 V | 5VSB | Power (AC) | PF/AC Volts |
|---|---|---|---|---|---|---|
| Idle | 12.143V | 5.034V | 3.349V | 5.138V | 6.03W | 0.458 |
| 115.1V | ||||||
| Standby | 0.11W | 0.016 | ||||
| 115.3V |
In the table above, you'll find the power consumption and voltage values of all rails (except minus 12V) when the PSU is idle (powered on, but without any load on its rails), and the power consumption when the PSU is in standby mode (without any load, at 5VSB).
Vampire power is low with 115VAC input and a tad higher with 230VAC, as usual. Overall, this unit has minimal energy demands in standby mode, which is good news for the environment as well as your wallet (especially in the long run).
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 (RPMs), and the delta between input and output temperature. The results were obtained at 36 °C (96.8 °F) to 45 °C (113 °F) ambient temperature.
The next chart shows the cooling fan's speed (RPMs) and output noise. We measured acoustics from one meter away, inside a small, custom-made anechoic chamber with internals completely covered in soundproofing material (be quiet! Noise Absorber kit). Background noise inside the anechoic chamber was below 18 dB(A) during testing, and the results were obtained with the PSU operating at 36 °C (96.8 °F) to 45 °C (113 °F) ambient temperature.
The following graph illustrates the fan's output noise over the entire operating range of the PSU. 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 Snow Silent unit honors the second part of its name, providing quiet operation throughout most of its operating range. The combination of a medium-speed FDB fan, semi-passive operation and the relaxed fan profile play a key role in this unit's decreased noise output. It's definitely a PSU that will please users who are sensitive to noise.
