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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 ACP-850FP7's efficiency at low loads, and loads from 10 to 110 percent of its maximum-rated capacity.
Compared to the high-end Corsair competition, which sports the same efficiency certifications, Aerocool's ACP-850FP7 fares well. It comes close under normal loads and takes a significant lead in light-load situations.
Efficiency At Low Loads
In the following tests, we measure the ACP-850FP7'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 | 1.196A | 0.493A | 0.471A | 0.195A | 19.647 | 75.302% | 0 RPM | <6.0 dB(A) | 0.800 |
| 12.192V | 5.054V | 3.372V | 5.048V | 26.091 | 115.21V | ||||
| 2 | 2.418A | 0.981A | 0.976A | 0.395A | 39.722 | 81.536% | 0 RPM | <6.0 dB(A) | 0.885 |
| 12.190V | 5.058V | 3.373V | 5.045V | 48.717 | 115.21V | ||||
| 3 | 3.644A | 1.478A | 1.479A | 5.042A | 59.873 | 86.238% | 0 RPM | <6.0 dB(A) | 0.921 |
| 12.190V | 5.058V | 3.372V | 5.042V | 69.428 | 115.21V | ||||
| 4 | 4.857A | 1.976A | 1.954A | 0.790A | 79.760 | 88.051% | 0 RPM | <6.0 dB(A) | 0.934 |
| 12.188V | 5.058V | 3.372V | 5.036V | 90.584 | 115.21V |
Under light loads, the ACP-850FP7's efficiency levels are jaw-dropping. With only 20W of load, our efficiency measurements exceed 75% while other "efficient" PSUs struggle to get above 70%.
Of course, the fan isn't active under such light loads, so noise is negligible. Our test sample didn't exhibit any coil whine, either.
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 at 5VSB under full load, or with 3A if its max current output on this rail 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 | 0.505 | 72.453% | 0.052 |
| 4.987V | 0.697 | 115.15V | ||
| 2 | 0.252A | 1.253 | 77.298% | 0.116 |
| 4.982V | 1.621 | 115.16V | ||
| 3 | 0.542A | 2.694 | 79.822% | 0.214 |
| 4.971V | 3.375 | 115.17V | ||
| 4 | 1.002A | 4.964 | 80.441% | 0.313 |
| 4.955V | 6.171 | 115.17V | ||
| 5 | 1.501A | 7.414 | 80.334% | 0.374 |
| 4.938V | 9.229 | 115.17V | ||
| 6 | 3.001A | 14.658 | 77.331% | 0.457 |
| 4.884V | 18.955 | 115.17V |
The 5VSB circuit's efficiency is acceptable, though it can't compete with CWT's implementation.
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 | 12.192V | 5.050V | 3.371V | 5.047V | 3.925 | 0.263 |
| 115.2V | ||||||
| Standby | 0.058 | 0.004 | ||||
| 115.2V |
Vampire power is very low with 115V, and it slightly exceeds 0.11W with 230V input.
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 37°C (98.6°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 hemi-anechoic chamber. Background noise inside the chamber was below 16.6 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 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 30°C (86°F) to 32°C (89.6°F).
Most of the time, the ACP-850FP7 remains in passive mode. That seems weird for an 850W PSU, but apparently high efficiency makes this possible without compromising reliability.
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