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Efficiency, Temperature & Noise
Our efficiency testing procedure is detailed here.
Using results from the previous page, we plotted a chart showing the SPR-0850F-R's efficiency at low loads, and loads from 10 to 110 percent of its maximum-rated capacity.
Thermaltake's SPR-0850F-R doesn't set any efficiency records, as you can see. It is actually only one step above the EVGA 850 BQ. However, we're comparing this unit to higher-end competitors, since low-efficiency 850W PSUs aren't particularly common nowadays.
Efficiency At Low Loads
In the following tests, we measure the SPR-0850F-R'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 #||12V||5V||3.3V||5VSB||DC/AC (Watts)||Efficiency||Fan Speed||Fan Noise||PF/AC Volts|
|1||1.190A||0.491A||0.477A||0.191A||19.683||61.886%||1295 RPM||33.8 dB(A)||0.705|
|2||2.406A||0.980A||0.987A||0.391A||39.800||73.283%||1300 RPM||33.9 dB(A)||0.867|
|3||3.620A||1.468A||1.496A||5.112A||59.857||79.726%||1390 RPM||35.2 dB(A)||0.922|
|4||4.832A||1.974A||1.979A||0.782A||79.811||81.458%||1400 RPM||35.4 dB(A)||0.955|
Under light loads, we observe very low efficiency. It's only when we hit 80W that this PSU manages to exceed the 80% mark. To add insult to injury, the SPR-0850F-R's fan spins at at high speeds, making enough noise to bother sensitive users.
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 more 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 maximum current output on that 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|
The 5VSB rail achieves good efficiency, especially if we take into account this PSU's overall performance.
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).
Vampire power is low with 115V. Meanwhile, it's higher than expected with 230V, given our 115V result.
Fan RPM, Delta Temperature, And Output Noise
Our mixed noise testing is described in detail here.
Our first chart 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 16.6 dB(A) during testing. It's actually quite a bit lower, but our sound meter's mic is at its limit there. The ambient temperature was between 37°C (98.6°F) to 47°C (116.6°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 SPR-0850F-R's fan makes its presence known from the start. At loads higher than 500W, the fan's noise exceeds 40 dB(A) and starts to get annoying. Beyond 650W, it's in the 43-46 dB(A) range and quite loud. In any case, you shouldn't expect a low-efficiency PSU with 850W capacity to be silent. After all, its fan has to cope with significant thermal loads.
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Aris Mpitziopoulos is a Contributing Editor at Tom's Hardware US, covering PSUs.
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