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Enermax D.F. 500W PSU Review

The Enermax D.F. 500W is a fully modular PSU featuring high efficiency, quiet operation, and individually sleeved cables. But are those enough to justify its premium price tag?

Efficiency, Temperature, And Noise


Our efficiency testing procedure is detailed here.

Using results from the previous page, we plotted a chart showing the EPF500AWT's efficiency at low loads, and loads from 10 to 110 percent of its maximum-rated capacity.

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This is a highly efficient PSU that had no trouble beating our comparison units, since the models we can include earned lower efficiency certifications. The only PSU that comes close is Bitfenix's BWG550M, which is based on a very good CWT platform.

Efficiency At Low Loads

In the following tests, we measure the EPF500AWT'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
11.207A0.491A0.475A0.191A19.7376.855%580 RPM20.8 dB(A)0.844
22.429A0.978A0.980A0.386A39.7285.084%580 RPM20.8 dB(A)0.918
33.660A1.473A1.485A5.120A59.8888.300%580 RPM20.8 dB(A)0.940
44.878A1.973A1.965A0.781A79.7789.794%580 RPM20.8 dB(A)0.961

The fan's noise is minimal in these tests, while efficiency is very high. In three out of the four metrics, efficiency registers way above 80%, and during the last one it's almost 90%.

5VSB Efficiency

The ATX specification states that 5VSB standby supply efficiency should be as high as possible, recommending 50 percent or higher with 100mA of load, 60 percent or higher with 250mA of load, and 70 percent or higher with 1A or more of load.

We take four measurements: one each at 100, 250, and 1000mA, 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 registers high efficiency, especially with 115V input.

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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Standby power consumption is very low, and the PSU has no trouble satisfying the ErP Lot 6 2013 requirements.

Fan RPM, Delta Temperature, And Output Noise

Our mixed noise testing is described in detail here.

The chart below illustrates the cooling fan's speed (in RPM), and the delta between input and output temperature. The results were obtained at 36°C (96.8°F) to 45°C (113°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 small, custom-made anechoic chamber with internals completely covered in sound-proofing material (be quiet! Noise Absorber kit). Background noise inside the chamber was below 18 dB(A) during testing, and the results were obtained with the PSU operating at 36°C (96.8°F) to 45°C (113°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 PSU is very quiet, although it doesn't feature a semi-passive mode. With a low-speed fan and a relaxed fan profile, there is no need for semi-passive operation.

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