Efficiency

Using the efficiency results from the previous page, we plotted a chart which shows the efficiency of the HX750i at low loads and at loads equal to 20% -100% of the PSU's maximum-rated load.



The unit's efficiency levels are amazing with both light and normal loads. In the graph for the latter, the HX750i even managed to surpass the flagship AX760i unit with digital control, not just a digital interface. This platform definitely has a lot of potential.

Efficiency at Low Loads

In the next tests, we measured the HX750i's efficiency 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 unit was both very efficient and completely inaudible. It manged to crack the 80% mark with only 40 W load, which is impressive for a 750 W unit.

Corsair Link Screenshots

Screenshots of the Corsair Link software follow. The order of the screenshots is the same as the order of the tests shown in the table above (low loads efficiency test #1 to test #4).

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.

Not top-notch since we didn't get a reading above 80% in the last test, the unit exhibited good 5VSB efficiency levels.

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).

A very low phantom-power reading since modern stand-by PWM controllers minimize energy consumption in standby nicely.

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 the output noise follows. We measure the fan's noise output 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 38°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.



This is a truly silent PSU, which completely confirms Corsair's statements. It only loses out to Corsair's RM750 PSU by a very small amount, taking second place in our noise chart with dozens of PSUs.

The following graph illustrates the fan's speed throughout the PSU's entire operating range. The ambient temperature was in-between 28°C and 30°C.



Under normal conditions, the fan's speed won't exceed 1000 RPM with even the full load, so the PSU's incredibly low noise output should come as no surprise.