Why you can trust Tom's Hardware Our expert reviewers spend hours testing and comparing products and services so you can choose the best for you. Find out more about how we test.
Efficiency, Temperature & Noise
Efficiency
We detail our efficiency testing procedure here.
Using results from the previous page, we plotted a chart showing the CX450’s efficiency at low loads and loads from 10 to 110 percent of its maximum-rated capacity.
Great Wall's platform was more efficient under normal and light loads.
Efficiency at Low Loads
In the following tests, we measured the CX450's efficiency at loads significantly lower than 10 percent of its maximum capacity (the lowest load the 80 PLUS standard measures). The loads we dialed were 20W, 40W, 60W and 80W. This is important for symbolizing when a PC is idle with power saving features turned on.
Corsair CX450 - Great Wall
| Test # | 12V | 5V | 3.3V | 5VSB | DC/AC (Watts) | Efficiency | Fan Speed | PSU Noise | PF/AC Volts |
|---|---|---|---|---|---|---|---|---|---|
| 1 | 1.197A | 0.499A | 0.478A | 0.198A | 19.535 | 68.672% | 1105 RPM | 24.0 dB(A) | 0.880 |
| 12.067V | 5.009V | 3.329V | 5.045V | 28.447 | 115.35V | ||||
| 2 | 2.455A | 0.999A | 0.990A | 0.397A | 39.928 | 80.127% | 1100 RPM | 24.0 dB(A) | 0.948 |
| 12.069V | 5.008V | 3.328V | 5.039V | 49.831 | 115.32V | ||||
| 3 | 3.649A | 1.495A | 1.472A | 5.032A | 59.420 | 83.556% | 1170 RPM | 26.1 dB(A) | 0.969 |
| 12.068V | 5.008V | 3.327V | 5.032V | 71.114 | 115.30V | ||||
| 4 | 4.910A | 1.997A | 1.982A | 0.796A | 79.834 | 85.380% | 1235 RPM | 27.7 dB(A) | 0.979 |
| 12.066V | 5.006V | 3.326V | 5.026V | 93.504 | 115.26V |
Efficiency under light loads was very high, especially for a mainstream 450W unit.
Corsair CX450 - CWT
| Test # | 12V | 5V | 3.3V | 5VSB | DC/AC (Watts) | Efficiency | Fan Speed | PSU Noise | PF/AC Volts |
|---|---|---|---|---|---|---|---|---|---|
| 1 | 1.211A | 0.493A | 0.483A | 0.196A | 19.686 | 64.915% | 818 RPM | 13.8 dB(A) | 0.930 |
| 12.060V | 5.057V | 3.299V | 5.075V | 30.326 | 115.14V | ||||
| 2 | 2.448A | 0.980A | 0.999A | 0.391A | 39.744 | 76.855% | 818 RPM | 13.8 dB(A) | 0.976 |
| 12.056V | 5.055V | 3.298V | 5.070V | 51.713 | 115.13V | ||||
| 3 | 3.685A | 1.478A | 1.514A | 5.064A | 59.863 | 80.657% | 818 RPM | 13.8 dB(A) | 0.983 |
| 12.052V | 5.053V | 3.296V | 5.064V | 74.219 | 115.13V | ||||
| 4 | 4.915A | 1.974A | 1.998A | 0.791A | 79.780 | 82.976% | 818 RPM | 13.8 dB(A) | 0.988 |
| 12.049V | 5.053V | 3.295V | 5.058V | 96.148 | 115.12V |
CWT's fan spun at a lower RPM (revolutions per minute), but the PSU's efficiency levels weren't as high as Great Wall's implementation.
5VSB Efficiency
The ATX specification (revision 1.4), along with CEC, ErP Lot 3 2014 and ErP Lot 6 2010/2013, states that 5VSB standby supply efficiency should be as high as possible, recommending 75 percent or higher with 550mA, 1A and 1.5A of load. The PSU should also achieve higher than 75 percent efficiency at 5VSB under full load, or with 3A if its max current output on this rail is higher than 3A.
We took six measurements: one each at 100mA, 250mA, 550mA, 1,000mA and 1,500mA and one with the full load the 5VSB rail can handle.
| Test # | 5VSB | DC/AC (Watts) | Efficiency | PF/AC Volts |
|---|---|---|---|---|
| 1 | 0.100A | 0.505 | 75.826% | 0.056 |
| 5.049V | 0.666 | 115.37V | ||
| 2 | 0.250A | 1.262 | 79.924% | 0.125 |
| 5.046V | 1.579 | 115.37V | ||
| 3 | 0.550A | 2.772 | 81.290% | 0.230 |
| 5.039V | 3.410 | 115.37V | ||
| 4 | 1.000A | 5.029 | 81.205% | 0.322 |
| 5.028V | 6.193 | 115.38V | ||
| 5 | 1.500A | 7.526 | 81.884% | 0.375 |
| 5.016V | 9.191 | 115.36V | ||
| 6 | 3.000A | 14.942 | 78.605% | 0.447 |
| 4.980V | 19.009 | 115.35V |
Great Wall's CX450 had a highly efficient 5VSB rail.
Power Consumption in Idle and Standby
The table below shows the power consumption and voltage values of all rails (except -12V) when the PSU was idle (powered on, but without any load on its rails) and the power consumption when the PSU was in standby mode (without any load, at 5VSB).
| Mode | 12V | 5V | 3.3V | 5VSB | Watts | PF/AC Volts |
|---|---|---|---|---|---|---|
| Idle | 12.094V | 5.007V | 3.329V | 5.050V | 13.314 | 0.682 |
| 115.4V | ||||||
| Standby | 0.067 | 0.006 | ||||
| 115.4V |
The power consumption of both CX450s was very low at idle.
Fan RPM, Delta Temperature & Output Noise
We describe our mixed noise testing in detail here.
The first chart below illustrates the cooling fan's speed in RPM, and the delta between input and output temperature. We obtained the results at 37°C (98.6°F) to 47°C (116.6°F) ambient temperature.
The next chart shows the cooling fan's speed in RPM and output noise. We measured acoustics from one meter away inside a hemi-anechoic (anechoic means non-echoing) chamber. Background noise inside the chamber was below 6 dB(A) during testing (it's actually much lower, but our sound meter’s microphone his its floor). We obtained the results with the PSU operating at 37°C (98.6°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 30°C (86°F) to 32°C (89.6°F).
Great Wall's CX450 wasn't particularly quiet, as you can see in the graph above. With 150W of load, the noise output was greater than 30 dB(A). Above 270W, it exceeded 40 dB(A).
CWT's CX450 had a much more relaxed fan profile. Up until 200W, its fan spun at low RPM. Even in a worst-case scenario, the noise output remained below 40 dB(A).
MORE: Best Power Supplies
MORE: How We Test Power Supplies
MORE: All Power Supply Content
