Efficiency

Using the efficiency results from the previous page, we plotted a chart that shows the Snow Silent-750's efficiency at low loads and loads equal to 20% -100% of the PSU's maximum-rated load.



The Snow Silent-750 achieved is very efficient with both light and normal loads. The fresh XP2S platform is among the best in this category, and although a very small efficiency percent was lost compared to the previous XP2 platform, we shouldn't forget the new design's significantly better load regulation.

Efficiency at Low Loads

In the next tests, we measured the efficiency of the Snow Silent-750 at loads much lower than 20% of its maximum-rated load (the lowest load the 80 Plus Standard measures). The loads we dialed were 40 W, 60 W, 80 W, and 100 W (for PSUs with over 500 W of capacity). This is important for settings where the PC is in idle mode with Power Saving turned on.

Efficiency at light loads was very high, well over 80% in all of our tests. The PSU also operated passively throughout these tests even though the temperature inside the hotbox was between 35°C-40°C.

5VSB Efficiency

The ATX specification states that 5VSB standby supply efficiency should be as high as possible and recommends 50% or higher efficiency with 100 mA of load, 60% or higher with 250 mA of load, and 70% or higher with 1 A or more of load.

We will take four measurements: one at 100, 250, and 1000 mA, each, and one with the full load the 5VSB rail can handle.

The 5VSB rail failed to impress us with its performance. We expected better results with at least one efficiency reading above the 80% mark.

Power Consumption in Idle & Standby

In the table below, you will find the power consumption and the voltage values of all rails (except -12V) when the PSU is in idle mode (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).

Easily meeting ErP Lot 6 2013 requirements, the unit consumes very little energy in standby.

Fan RPM, Delta Temperature & Output Noise

The cooling fan's speed (RPMs) and the delta difference between input and output temperature are illustrated in the following chart. The following results were obtained at 38°C-45°C ambient.



A chart that shows the cooling fan's speed (RPMs) and its output noise follows. We measure the fan's noise from one meter away, inside a small custom-made anechoic chamber whose internals are completely covered in specialized soundproofing material (Be Quiet! Noise Absorber Kit). Background noise inside the anechoic chamber was below 20 dBA during testing, and the results were obtained with the PSU operating at 38°C-45°C ambient.



The following graph illustrates the fan's output noise throughout the PSU's entire operating range. The same conditions as for the above graph apply to our measurements, but the ambient was in-between 28°C and 30°C.



Semi-passive mode lasts pretty long at normal ambient temperatures, and the fan doesn't produce much noise with even the full load. The PSU is very quiet at up to around 550 W since its fan won't produce more than 40 dBA in even our worst-case scenario.