Seasonic Focus Plus Gold 850 PSU Review

Efficiency, Temperature & Noise


Our efficiency testing procedure is detailed?here.

Using results from the previous page, we plotted a chart showing the SSR-850FX's efficiency at low loads, and loads from 10 to 110 percent of its maximum-rated capacity.

Efficiency-wise, Seasonic's SSR-850FX performs well! It takes first place under normal loads, and under light loads it lands in second.

Efficiency At Low Loads

In the following tests, we measure the SSR-850FX'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 Speed
PSU Noise
PF/AC Volts
11.273A0.500A0.482A0.197A20.56269.035%0 RPM
<6.0 dB(A)
22.456A1.001A0.995A0.393A40.12379.750%0 RPM<6.0 dB(A)0.915
33.709A1.499A1.507A5.089A60.53584.325%0 RPM<6.0 dB(A)0.954
44.895A1.999A1.986A0.788A80.03386.626%0 RPM<6.0 dB(A)0.971

It would be nice to see greater than 70% efficiency with 20W load. But we can't complain much about the 69.035% we actually recorded. The SSR-850FX operates passively at all four load levels, so output noise is obviously negligible.

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

The 5VSB rail achieves decent efficiency levels. But given this platform's overall performance, that 5VSB circuit isn't as impressive as the other rails. Seasonic should really seek to improve it.

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

Vampire power is pretty low under both voltage inputs.

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 47°C (116.6°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 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 30°C (86°F) to 32°C (89.6°F).

The semi-passive mode doesn't last long once the minor rails are pushed hard, something that happens in our cross-load tests. Still, noise remains below 30 dB(A) at up to ~580W load, and it exceeds 45 dB(A) with higher than 720W loads.

MORE: Best Power Supplies

MORE: How We Test Power Supplies

MORE: All Power Supply Content

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