Efficiency

Using the efficiency results from the previous page, we plotted a chart showing efficiency of the GT-700SG at low loads and at loads equal to 20-110% of the PSU's maximum rated load.



For a discussion of these results, see the text at the end of the previous page.

Efficiency at Low Loads

In the next tests, we measured the efficiency of the GT-700SG at loads much lower than 20% of its maximum rated load (the lowest load that the 80 Plus Standard measures). The loads that we dialed were 40, 60, 80, 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, efficiency was very good given that this PSU is Gold and not Platinum certified. The fan's speed was, on top of that, kept at low levels, so the output noise was kept at low levels as well (at least for our ears).

5VSB Efficiency

The ATX spec states that the 5VSB standby supply's 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 that the 5VSB rail can handle.


At 5VSB, efficiency starts rather high with an impressive 66%, with only 0.1 A load on this rail, but it fails to keep up the same pace on the last two tests. That said, an 77% reading is not considered low for the standards of this rail.

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).


We found the culprit for the extra-high efficiency on the 5VSB rail at low loads: the low vampire power of only 0.14 W. As it seems, the modern standby PWM controllers do an excellent job.

Fan RPM, Delta Temperature and 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 from 1 meter away inside a custom made, mini, anechoic chamber, which is totally covered internally by specialized soundproofing material (Be Quiet! Noise Absorber Kit). The background noise inside the anechoic chamber was below 30 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 entire operating range of the PSU. The same conditions of the above graph apply to our measurements, but the ambient in this case was between 28 and 32°C.