Efficiency

Using the efficiency results from the previous page, we plotted a chart showing the efficiency of the AX1500i at low loads and at loads equal to 20% -110% of the PSU's maximum-rated load.



As expected, the AX1500i crushes the competition, in both high and low loads, where normally it shouldn't be among the best-performing unit because of its monstrous capacity. But its digital control circuits apparently work wonders.

Efficiency at Low Loads

In the next tests, we measured the efficiency of the AX1500i 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.

For a unit with 1.5 kW capacity, the AX1500i was unexpectedly efficient at low loads, managing to stay well above 70% with 40 W load and near 89% with 100 W load.

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 above table (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.

The 5VSB rail's voltage regulation may not be that tight, which isn't that important for this particular rail, but its efficiency is high enough to easily meet the energy requirements of the ATX spec.

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 on 5VSB).

This monster's power consumption is dead-low at idle, close to 1/4th the limit.

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-49°C ambient.



A chart that shows the cooling fan's speed (RPMs) and its 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-49°C ambient.



The following graphs illustrates the fan's output noise and speed 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.



Considering this unit's huge capacity, output noise was kept at very low levels under normal conditions, which is due to the low RPM fan. Restricted energy losses also played a key role since they kept the thermal load to a minimum. Thermal loads obviously decrease as efficiency increases, which is a huge boon because it allows for slower and quieter cooling fans to be used.



At worst, the fan speed spun at 1200-1400 RPM, which would have been impossible with a 1.5 kW PSU a few months ago.