Test Setup

All measurements were performed using two Chroma 6314A mainframes equipped with the following electronic loads: six 63123A [350 W each], one 63102A [100 W x2], and one 63101A [200 W]. The aforementioned equipment is able to deliver 2500 W of load, and all loads are controlled by a custom-made software. We also used a Picoscope 3424 oscilloscope, a Picotech TC-08 thermocouple data logger, a Fluke 175 multimeter, and a Yokogawa WT210 power meter. We also included a wooden box, which, along with some heating elements, was used as a hot box. Finally, we had at our disposal four more oscilloscopes (Rigol 1052E and VS5042, Stingray DS1M12, and a second Picoscope 3424), and a CEM DT-8852 sound level meter. You will find more details about our equipment and the review methodology we follow in this article. Finally, we conduct all of our tests at 40°C-45°C ambient in order to simulate with higher accuracy the environment seen inside a typical system, with 40°C-45°C being derived from a standard ambient assumption of 23°C and 17°C-22°C being added for the typical temperature rise within a system.

Primary Rails Voltage Regulation

The following charts show the voltage values of the main rails, recorded over a range from 60 W to the maximum specified load, and the deviation (in percent) for the same load range.

5VSB Regulation

The following chart shows how the 5VSB rail deals with the load we throw at it.

Hold-up Time

Hold-up time is a very important PSU characteristic and represents the amount of time, usually measured in milliseconds, a PSU can maintain output regulations as defined by the ATX spec without input power. In other words, it is the amount of time the system can continue to run without shutting down or rebooting during a power interruption. The ATX spec sets the minimum hold-up time to 16 ms with the maximum continuous output load. In the following screenshot, the blue line is the mains signal and the yellow line is the "Power Good" signal. The latter is de-asserted to a low state when any of the +12V, 5V, or 3.3V output voltages fall below the undervoltage threshold, or after the mains power has been removed for a sufficiently long time to guarantee that the PSU cannot operate anymore.



The hold-up time was pretty long, significantly exceeding the minimum allowed time the ATX spec sets. This is incredibly surprising given the small combined capacity of the hold-up caps. The unit's ACRF topology apparently allows for high hold-up times with even small bulk caps.

Inrush Current

Inrush current or switch-on surge refers to the maximum, instantaneous input-current drawn by an electrical device when first turned on. Because of the charging current of the APFC capacitor(s), PSUs produce large inrush-current right as they are turned on. Large inrush current can cause the tripping of circuit breakers and fuses and may also damage switches, relays, and bridge rectifiers; as a result, the lower the inrush current of a PSU right as it is turned on, the better.



The hold up caps' relatively small total capacity resulted in currently the second-lowest inrush current we have ever measured in a 1 kW PSU. This is obviously good news since it ensures electrical components are not put under a lot of duress.

Voltage Regulation and Efficiency Measurements

The first set of tests revealed the stability of the voltage rails and the efficiency of the Power Zone 1000 W. The applied load was equal to (approximately) 20%, 40%, 50%, 60%, 80%, 100%, and 110% of the maximum load the PSU can handle. We conducted two additional tests. In the first test, we stressed the two minor rails (5V and 3.3V) with a high load while the load at +12V was only 0.10 A. This test reveals whether the PSU is Haswell ready or not. In the second test, we dialed the maximum load the +12V rail could handle while the load on the minor rails was minimal.

Contrary to other ACRF implementations we have tested so far, the Power Zone 1000 W achieved a really tight voltage regulation at +12V. FSP obviously improved their design and boosted its performance. Voltage regulation on the minor rails may not be impressive, but is still within 3%.

The PSU exhibited really nice efficiency which never reflected its official efficiency certification. Its efficiency looked much more like that of a Gold unit, not a Bronze one. We then wonder why be quiet! never tried to achieve the Gold or even Silver certification. That said, we noticed that the sample listed on the 80 Plus site had much lower efficiency than our sample at full load, while all other values were close to the values we measured in our corresponding load tests. FSP probably implemented modifications in their more recent batches of Power Zone PSUs to boost efficiency, which would explain the large difference between our measurements and those of the 80 Plus organization. Well, we believe that the PSU's Bronze certification will be a great marketing con since most users rely on the official efficiency rating without paying much attention to the results obtained in various reviews like this one.

The unit also had no problem whatsoever in delivering its full power at 46°C, but at such high operating temperatures, its fan was far from quiet, which contradicts be quiet!'s tradition and name. We definitely don't expect a 1 kW, Bronze-certified unit to be whisper quiet at full load and under such tough conditions, but be quiet! could have used a quieter fan to keep output noise below 50 dBA.