be quiet! System Power U9 700W PSU Review

1. Introduction2. Packaging, Contents & Exterior3. Teardown & Component Analysis4. Load Regulation, Hold-Up Time & Inrush Current5. Efficiency, Temperature & Noise6. Protection Features & DC Power Sequencing7. Cross-Load Tests & Infrared Images8. Transient Response Tests9. Ripple Measurements10. EMC Pre-Compliance Testing11. Performance, Value, Noise & Efficiency12. Final Analysis13. View All Pages

Efficiency

Our efficiency testing procedure is detailed here.

Using results from the previous page, we plotted a chart showing the SU9-700’’s efficiency at low loads, and loads from 10 to 110 percent of its maximum-rated capacity.

The efficiency under normal loads is high enough, always for the standards of this category, while with light loads it isn't so competitive.

Efficiency At Low Loads

In the following tests, we measure the SU9-700’'s efficiency at loads significantly lower than 10 percent of its maximum capacity (the lowest load the 80 PLUS standard measures). The loads we dial are 20, 40, 60, and 80W. This is important for representing when a PC is idle, with power-saving features turned on.

Test #	12V	5V	3.3V	5VSB	DC/AC (Watts)	Efficiency	Fan Speed (RPM)	PSU Noise (dB[A])	PF/AC Volts
1	1.179A	0.498A	0.482A	0.197A	19.452	69.313%	622	9.8	0.871
	12.175V	5.018V	3.313V	5.084V	28.064				115.34V
2	2.429A	0.997A	0.994A	0.394A	39.860	76.474%	618	9.7	0.926
	12.172V	5.016V	3.312V	5.078V	52.122				115.31V
3	3.615A	1.495A	1.479A	5.072A	59.391	81.484%	618	9.7	0.962
	12.170V	5.015V	3.311V	5.072V	72.887				115.28V
4	4.869A	1.994A	1.995A	0.790A	79.850	84.122%	638	10.2	0.962
	12.168V	5.014V	3.310V	5.066V	94.922				115.25V

The fan's speed is kept low under light loads while the efficiency levels are not that high. But this is an older generation design destined for users on a tight budget, so we shouldn't expect for wonders here.

5VSB Efficiency

The ATX specification (revision 1.4), along with CEC, ErP Lot 3 2014 and ErP Lot 6 2010/2013, states that the 5VSB standby supply efficiency should be as high as possible, recommending 75 percent or higher with 550mA, 1A, and 1.5A of load.

The supply 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 #	5VSB	DC/AC (Watts)	Efficiency	PF/AC Volts
1	0.100A	0.509	77.356%	0.051
	5.088V	0.658		115.37V
2	0.250A	1.272	79.649%	0.117
	5.085V	1.597		115.37V
3	0.550A	2.794	80.380%	0.221
	5.080V	3.476		115.37V
4	1.000A	5.072	81.126%	0.315
	5.072V	6.252		115.37V
5	1.500A	7.595	79.570%	0.377
	5.063V	9.545		115.36V
6	3.000A	15.111	78.662%	0.453
	5.037V	19.210		115.35V

The 5VSB rail registers high efficiency even under very light loads. It is nice to see a budget-oriented platform with a good standby circuit.

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 unit is in standby mode (without any load, at 5VSB).

Mode	12V	5V	3.3V	5VSB	Watts	PF/AC Volts
Idle	12.168V	5.022V	3.316V	5.088V	5.213	0.359
						115.4V
Standby					0.044	0.003
						115.4V

The vampire power is kept low with both voltage inputs. This is why the 5VSB rail achieves high efficiency under super light loads.

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 35°C (95°F) to 41°C (105.8°F) ambient temperature.

The next chart shows the cooling fan's speed (again, in RPM) and output noise. We measure acoustics from one meter away, inside a hemi-anechoic chamber. Background noise inside the chamber is below 6 dB(A) during testing (it's actually much lower, but our sound meter’s microphone hits its floor), and the results are obtained with the PSU operating at 35°C (95°F) to 41°C (105.8°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 is between 30°C (86°F) to 32°C (89.6°F).

For the majority of its operational range the unit's output noise remains at very low levels, thanks to the highly relaxed fan profile.

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