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be quiet! SFX L Power 600W PSU Review

Efficiency, Temperature & Noise


Our efficiency testing procedure is detailed here.

Using results from the previous page, we plotted a chart showing the SFX L Power 600W's efficiency at low loads, and loads from 10 to 110 percent of its maximum-rated capacity.

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Under normal loads, this platforms achieves a high overall efficiency score. Meanwhile, it lands around the middle of the pack with light loads.

Efficiency At Low Loads

In the following tests, we measure the SFX L Power 600W's efficiency at loads significantly lower than 10 percent of its maximum capacity (the lowest load the 80 PLUS standard measures). The loads we dialed were 20, 40, 60, and 80W. This is important for representing when a PC is idle, with power-saving features turned on.

Test #12V5V3.3V5VSBDC/AC (Watts)EfficiencyFan SpeedFan NoisePF/AC Volts
11.195A0.492A0.471A0.196A19.70466.381%1270 RPM24.8 dB(A)0.914
22.411A0.980A0.973A0.396A39.75078.721%1270 RPM24.8 dB(A)0.956
33.621A1.477A1.481A5.035A59.86784.091%1365 RPM26.5 dB(A)0.972
44.829A1.975A1.955A0.796A79.75486.268%1365 RPM26.5 dB(A)0.983

With 20W load, we would like to see over 70% efficiency. At 40W, it'd be great to calculate 80% efficiency. However, this PSU can't quite get there. In addition, its fan spins fast to facilitate decent airflow. We run these tests at >36°C, after all. Fortunately, noise output remains low.

5VSB Efficiency

The ATX specification, along with CEC, ErP Lot 3 2014 and ErP Lot 6 2010/2013, states that 5VSB standby supply efficiency should be as high as possible, recommending 75 percent or higher with 550mA, 1A, and 1.5A of load. The PSU should also achieve higher than 75% efficiency at 5VSB under full load, or with 3A if its max current output on this rail is higher than 3A.

We take six measurements: one each at 100, 250, 550, 1000, and 1500mA, and one with the full load the 5VSB rail can handle.

Test #5VSBDC/AC (Watts)EfficiencyPF/AC Volts
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The 5VSB rail's efficiency levels are good, given that we see one reading over 80% and two others in the same neighborhood.

Power Consumption In Idle And Standby

In the table below, you'll find the power consumption and voltage values of all rails (except -12V) when the PSU is idle (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).

Mode12V5V3.3V5VSBWattsPF/AC Volts
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Vampire power is low with 115V and 230V input.

Fan RPM, Delta Temperature, And Output Noise

Our mixed noise testing is described in detail here.

The first chart below illustrates the cooling fan's speed (in RPM), and the delta between input and output temperature. The results were obtained at 37°C (98.6°F) to 46°C (114.8°F) ambient temperature.   

The next chart shows the cooling fan's speed (again, in RPM) and output noise. We measured acoustics from one meter away, inside a hemi-anechoic chamber. Background noise inside the chamber was below 6 dB(A) during testing (it's actually much lower, but our sound meter’s microphone hits its floor), and the results were obtained with the PSU operating at 37°C (98.6°F) to 46°C (114.8°F) ambient temperature. 

The following graph illustrates the fan's output noise over the PSU's operating range. The same conditions of the above graph apply to our measurements, though the ambient temperature was between at 30°C (86°F) to 32°C (89.6°F).  

The 120mm fan spins slowly at up to 200W loads. Between 200W and 300W on the +12V rail, the PSU's noise output is below 25 dB(A). The 30 dB(A) mark is passed with 500W+ loads and up.

All in all, the fan profile is relaxed given this PSU's compact dimensions.

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Aris Mpitziopoulos
Aris Mpitziopoulos is a Contributing Editor at Tom's Hardware US, covering PSUs.