Efficiency

Using the efficiency results from the previous page, we plotted a chart that shows the ST60F-ESB's efficiency at low loads and loads equal to 20% -110% of the PSU's maximum-rated load.



Compare the unit to the other PSUs in the graph and things don't look so good at low loads, although it performed much better with normal loads by beating out most Bronze PSUs in its price range.

Efficiency at Low Loads

In the next tests, we measured the efficiency of the ST60F-ESB 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 a capacity over 500 W). This is important for settings where the PC is in idle mode with Power Saving turned on.

With 40 W load, efficiency was very low and dangerously close to 70%, but the PSU achieved significantly higher efficiency ratings in the other three tests. Fan noise also remained very low in these tests despite the high ambient temperature inside the hotbox.

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.

Although full-load efficiency dropped a little in the third load test, which shows that 2.5 A are on the verge for this circuit and design, the 5VSB rail performed fairly well given this is a budget PSU.

Power Consumption in Idle & Standby

The table below holds 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) and the power consumption values when the PSU is in standby mode (without any load on 5VSB).

Power consumption is much lower than 0.5 W in standby, so all is good here.

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 an ambient temperature of 38°C-45°C.



A chart that shows the cooling fan's speed (RPMs) and the output noise follows. We measure the fan's noise from 1 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 30 dBA during testing, and the results were obtained with the PSU operating at an ambient temperature of 38°C-45°C.



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



This PSU cannot be described as quiet at even below an ambient temperature of 30°C, and it is definitely noisy with typical loads and above.