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Efficiency, Temperature & Noise
Efficiency
Our efficiency testing procedure is detailed here.
Using results from the previous page, we plotted a chart showing the HX1200's efficiency at low loads, and loads from 10 to 110 percent of the PSU's maximum-rated capacity.
Under normal loads, the HX1200 achieves nearly the same efficiency as Corsair's HX1200i, while under light loads, the difference is notable (favoring the higher-end model).
Efficiency At Low Loads
In the following tests, we measure the HX1200'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 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 | Fan Noise | PF/AC Volts |
|---|---|---|---|---|---|---|---|---|---|
| 1 | 1.202A | 0.493A | 0.477A | 0.197A | 19.699 | 62.362% | 0 RPM | <6.0 dB(A) | 0.893 |
| 12.179V | 5.040V | 3.319V | 5.036V | 31.588 | 115.11V | ||||
| 2 | 2.422A | 0.990A | 0.992A | 0.396A | 39.765 | 76.011% | 0 RPM | <6.0 dB(A) | 0.944 |
| 12.176V | 5.039V | 3.319V | 5.031V | 52.315 | 115.12V | ||||
| 3 | 3.650A | 1.476A | 1.504A | 5.028A | 59.861 | 82.073% | 0 RPM | <6.0 dB(A) | 0.967 |
| 12.175V | 5.038V | 3.320V | 5.028V | 72.936 | 115.12V | ||||
| 4 | 4.866A | 1.984A | 1.984A | 0.796A | 79.816 | 85.267% | 0 RPM | <6.0 dB(A) | 0.973 |
| 12.173V | 5.038V | 3.320V | 5.025V | 93.607 | 115.12V |
With 20W load, the PSU barely exceeds 60% efficiency. Under 40W load, it doesn't even get to 80%. It's only during the last two tests that Corsair's HX1200 passes the 80% mark.
5VSB Efficiency
The ATX specification, 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% efficiency under full load, or with 3A if its maximum current output at 5VSB is higher than 3A.
We take six measurements: one each at 100, 250, 550, 1000, and 1500mA, and one with the full load the 5VSB rail can handle.
| Test # | 5VSB | DC/AC (Watts) | Efficiency | PF/AC Volts |
|---|---|---|---|---|
| 1 | 0.101A | 0.509 | 76.657% | 0.065 |
| 5.016V | 0.664 | 115.12V | ||
| 2 | 0.252A | 1.262 | 80.949% | 0.146 |
| 5.013V | 1.559 | 115.12V | ||
| 3 | 0.542A | 2.715 | 81.679% | 0.269 |
| 5.010V | 3.324 | 115.13V | ||
| 4 | 1.002A | 5.012 | 81.364% | 0.387 |
| 5.001V | 6.160 | 115.14V | ||
| 5 | 1.502A | 7.494 | 80.929% | 0.453 |
| 4.990V | 9.260 | 115.14V | ||
| 6 | 3.502A | 17.342 | 80.317% | 0.532 |
| 4.952V | 21.592 | 115.14V |
The 5VSB rail is highly efficient. CWT pays a lot of attention to this circuit and we like to point it out, since there are still manufacturers that don't care as much as they should about 5VSB efficiency.
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 the PSU is in standby mode (without any load, at 5VSB).
| Mode | 12V | 5V | 3.3V | 5VSB | Watts | PF/AC Volts |
|---|---|---|---|---|---|---|
| Idle | 12.184V | 5.044V | 3.321V | 5.041V | 11.036 | 0.626 |
| 115.1V | ||||||
| Standby | 0.036 | 0.004 | ||||
| 115.1V |
Vampire power is as low as can be with both 115V and 230V voltage input.
Fan RPM, Delta Temperature, And Output Noise
Our mixed noise testing is described in detail here.
The chart below illustrates the cooling fan's speed (in RPM), and the delta between input and output temperature. The results were obtained at 37°C (98.6°F) to 46°C (114.8°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 hemi-anechoic chamber. Background noise inside the chamber was below 6 dB(A) during testing (it's actually much lower, but our sound meter’s microphone hits its floor), and the results were obtained with the PSU operating at 37°C (98.6°F) to 46°C (114.8°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 30°C (86°F) to 32°C (89.6°F).
Because we tax the minor rails right out of the gate, Corsair's passive mode doesn't last long in these tests. Still, the PSU is very quiet, particularly in light of its huge capacity. The fan's noise exceeds 30 dB(A) only when the load exceeds 950W.
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