Efficiency, Temperatures And Noise
Our efficiency testing procedure is detailed here.
Using the previous page's results, we plotted a chart showing the efficiency of the Dark Power P11-850 at low loads, and at loads equal to 10 to 110 percent of the PSU's maximum rated capacity.
The Dark Power P11-850 took the lead in efficiency performance over all the competing PSUs under normal loads, including Corsair's AX860 and AX860i, which many consider among the best in this wattage category. Under light loads, the PSU performed pretty well, though it fell behind the Seasonic implementations (Corsair AX860 and Cooler Master V850).
Efficiency At Low Loads
In the next tests, we measure the efficiency of the Dark Power P11-850 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.
The Dark Power Pro 11 delivered high efficiency levels at light loads, with two out of the four tests easily exceeding the 80-percent mark. In addition, the output noise was almost inaudible.
The ATX specification states that 5VSB standby supply efficiency should be as high as possible, recommending 50 percent or higher efficiency with a 100mA load, 60 percent or higher with a 250mA load and 70 percent or higher with a 1A or higher load.
We will take four measurements: one each at 100, 250 and 1000mA, and one with the full load the 5VSB rail can handle.
The 5VSB rail wasn't so efficient. At 115V input, we would like to see at least one reading above 80 percent. At 230V, this PSU fell to the bottom of the pack.
Power Consumption In Idle And Standby
In the table above, you find the power consumption and voltage values of all rails (except -12V) when the PSU is in idle mode (powered on, but without any load on its rails). You also find the power consumption when the PSU is in standby mode (without any load at 5VSB).
Power consumption at idle was low, with both 115V and 230V input.
Fan RPM, Delta Temperature And Output Noise
Our mixed noise testing is described in detail here.
The following chart illustrates the cooling fan's speed (RPMs) and the delta between input and output temperature. The results were obtained at 36 degrees C to 46 degrees C ambient temperature.
The next chart shows the cooling fan's speed (RPMs) and output noise. We measured acoustics from one meter away inside of 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 degrees C to 46 degrees C 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 28 degrees C and 30 degrees C.
At normal conditions, the PSU is dead silent, as you can see from the graph above. Even with full load, the noise that the PSU's fan outputs is within the 31-34 dB(A) region, a low level for a 850W PSU.