Efficiency

Using the efficiency results on the previous page, we plotted a chart to show the Fortress-750's efficiency at low loads and at loads equal to 20% -100% of the PSU's maximum-rated load.



The unit scored high efficiency results that easily compare to the competition, with both low and high loads. Check the normal loads efficiency graph and you will notice that only four high-end platforms managed to beat the Fortress-750, with two of them far more expensive digital units.

Efficiency at Low Loads

In the next tests, we measured the efficiency of the Fortress-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.

At low loads, the Fortress-750 achieved high overall efficiency levels, with three out of its four readings well over the 80% mark.

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.

While the 5VSB rail is not that strong, it did well enough in terms of efficiency. It is also nice to see Platinum units score more than 80% efficiency on this rail, which is much easier said than done. You see, this rail usually uses conventional SBRs, so 80% efficiency is, contrary to other rails, considered a pretty high reading.

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).

Vampire power was at around half the limit the ErP Lot 6 2013 directive sets.

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 37°C-45°C ambient.



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 20 dBA during testing, and the results were obtained with the PSU operating at 37°C-45°C ambient.



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 in-between 28°C and 30°C.



As the above graph depicts, this PSU is quiet enough while operating under normal conditions. Output noise was at 28-31 dBA at up to 550 W load, which makes many system components, like case fans and AIO liquid coolers, noisier than the PSU.