EVGA SuperNOVA 850 P2 Power Supply Review

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 EVGA SuperNOVA 850 P2's efficiency under low loads, and loads from 10 to 110 percent of the PSU's maximum-rated capacity.

This is a highly efficient PSU throughout its load range; the graphs above clearly show this.

Efficiency At Low Loads

In the following tests, we measure the 850 P2's efficiency under 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.

With only 20W load, efficiency drops below 70 percent. However, with 40W of load it goes above 79 percent, and in the last two tests the unit easily passes the 80 percent mark. We would like to see greater than 70 percent efficiency in the first test, but obviously Super Flower's engineers preferred to tune this PSU for better efficiency at higher loads.

5VSB Efficiency

The ATX specification states that 5VSB standby supply efficiency should be as high as possible, recommending 50 percent or higher 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. 

Efficiency at 5VSB isn't high enough, especially for a Platinum-rated PSU and taking into account the rail's low amperage.

Power Consumption In Idle And Standby

In the table above, 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).

Vampire power is very low, as usually is the case in modern PSUs equipped with dedicated standby PWM controllers.

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 49 °C (120.2 °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 37 °C (98.6 °F) to 49 °C (120.2 °F) ambient temperature. 

The following graph illustrates the fan's output noise over the PSU's entire 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).  

With ECO mode enabled and under normal operating conditions, the fan won't spin under loads of up to 340W. And even when it is engaged, it spins slowly. Expect low output noise as a result. In general, this is a very quiet PSU that'll satisfy enthusiasts who hate loud PC parts.