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 850 BQ's efficiency at low loads, and loads from 10 to 110 percent of its maximum-rated capacity.
The efficiency difference between 115V and 230V is quite large. Usually it is around 2%, but in this PSU it reaches an impressive 2.71%. Compared to other Bronze-rated units, the 850 BQ takes the lead from Corsair's CX750M and is notably behind the CX650M.
Efficiency At Low Loads
In the following tests, we measure the 850 BQ'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 | 1.187A | 0.480A | 0.467A | 0.195A | 19.59 | 61.07% | 1120 RPM | 38.8 dB(A) | 0.943 |
| 12.261V | 5.116V | 3.421V | 5.056V | 32.08 | 115.1V | ||||
| 2 | 2.404A | 0.968A | 0.965A | 0.396A | 39.70 | 71.79% | 1120 RPM | 38.8 dB(A) | 0.972 |
| 12.254V | 5.108V | 3.416V | 5.047V | 55.30 | 115.1V | ||||
| 3 | 3.625A | 1.465A | 1.465A | 5.037A | 59.86 | 77.14% | 1120 RPM | 38.8 dB(A) | 0.973 |
| 12.247V | 5.100V | 3.410V | 5.037V | 77.60 | 115.1V | ||||
| 4 | 4.833A | 1.964A | 1.936A | 0.795A | 79.75 | 80.47% | 1120 RPM | 38.8 dB(A) | 0.984 |
| 12.239V | 5.094V | 3.405V | 5.029V | 99.11 | 115.2V |
The fan's speed is insanely high for such light loads. If you want a silent PSU, you'd better stay away from this one. Moreover, the efficiency levels are quite disappointing under loads lower than 60W. It's only during the last test that the 850 BQ passes 80% efficiency.
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 | 73.24% | 0.096 |
| 5.060V | 0.71 | 115.1V | ||
| 2 | 0.252A | 1.27 | 76.05% | 0.195 |
| 5.056V | 1.67 | 115.1V | ||
| 3 | 1.002A | 5.05 | 78.54% | 0.352 |
| 5.035V | 6.43 | 115.1V | ||
| 4 | 3.002A | 14.98 | 76.98% | 0.432 |
| 4.991V | 19.46 | 115.1V |
The 5VSB rail's efficiency is decent given this unit's entry-level efficiency certification.
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 | 12.247V | 5.121V | 3.433V | 5.061V | 7.15 | 0.609 |
| 115.1V | ||||||
| Standby | 0.05 | 0.007 | ||||
| 115.1V | ||||||
Phantom power is very low with both voltage inputs.
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 33°C (91.4°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 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 33°C (91.4°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 28°C (82.4°F) to 30°C (86°F).
The PSU could be much quieter with a proper fan profile. However, HEC decided to increase its reliability by making the fan spin at 1120 RPM, minimum. With loads higher than 600W, and even under normal temperature conditions, you will probably need ear plugs to tolerate the fan's noise.