Efficiency

Using the efficiency results from the previous page, we plotted a chart showing efficiency of the Power Zone 850 W at low loads and at loads equal to 20%-110% of the PSU's maximum-rated load.



The Power Zone did pretty well at both low and normal loads as it is only hinges behind the Gold-certified competition a tiny bit. The unit could easily clear 80 Plus Silver requirements, and we don't understand why it only has a Bronze certification. be quiet! probably sent an early production model with significantly lower efficiency to the 80 Plus organization (Ecova Plug Load Solutions) for certification.

Efficiency at Low Loads

In the next tests, we measured the efficiency of the Power Zone 850 W at loads much lower than 20% of its maximum rated load (the lowest load the 80 Plus Standard measures). The loads we dialed were 40 W, 60 W, 80 W, and 100 W (for PSUs with a capacity over 500 W). This is important for settings where the PC is in idle mode with Power Saving turned on.

The PSU managed to impress us with its high efficiency at low loads, including a mere load of 40 W. The fan also spun at low enough RPM throughout these tests, which kept noise at a minimum despite the high ambient inside the hot box.

5VSB Efficiency

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

We will take four measurements: one at 100, 250, and 1000 mA, each, and one with the full load the 5VSB rail can handle.

The 5VSB rail wasn't that efficient, and efficiency definitely dropped significantly at full load, which shows us that the 3A it provides are on the verge of what its circuit can handle.

Power Consumption in Idle & Standby

In the table below, you will find the power consumption and the voltage values of all rails (except -12V) when the PSU is in idle mode (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).

Like every PSU we have tested over the last couple years, this one too easily meets the ErP Lot 6 2013 requirements as it consumes much less than 0.5 W of power in standby.

Fan RPM, Delta Temperature & Output Noise

The cooling fan's speed (RPMs) and the delta difference between input and output temperature are illustrated in the following chart. The following results were obtained at 37°C-45°C ambient.



A chart that shows the cooling fan's speed (RPMs) and the output noise follows. We measure the fan's noise from 1 meter away, inside a small custom-made anechoic chamber whose internals are completely covered in specialized soundproofing material (Be Quiet! Noise Absorber Kit). Background noise inside the anechoic chamber was below 30 dBA during testing, and the results were obtained with the PSU operating at 37°C-45°C ambient.



The following graph illustrates the fan's output noise throughout the PSU's entire operating range. The same conditions of the above graph apply to our measurements, but the ambient temperature was between 28°C and 30°C.



Definitely not the quietest PSU be quiet! offers, its performance in this area doesn't match the company's tradition mostly because the Power Zone 850 W's design demands for a lot of airflow inside the case, which inevitably increases noise output. If you plan to have it operate at typical loads most of the time, it can be quiet enough, but its noise output will annoy you at higher loads, especially with high ambient temperatures thrown into the mix.