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Be Quiet! Dark Power Pro 11 1200W PSU Review

be quiet! says it's committed to building silent products, including the company's top PSU line, the Dark Power Pro 11. In this review, we will put the 1200 W Dark Power Pro 11 model to the test, which promises good performance and silent operation.

Load Regulation, Hold-Up Time And Inrush Current

To learn more about our PSU tests and methodology, please check out How We Test Power Supply Units. 

Primary Rails And 5VSB Load Regulation

Load Regulation testing is detailed here.

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Hold-Up Time

Our hold-up time tests are described in detail here.

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The hold-up time that our equipment measured was lower than 16 ms, so the PSU failed in this test.

Inrush Current

For details on our inrush current testing, please click here.

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The registered inrush current was adequate, especially for a 1.2 kW unit. This is great news, but we would prefer to see a little higher inrush current, which could be possible if be quiet! used higher capacity hold-up caps, instead of a hold-up time lower than 16 ms.

Load Regulation And Efficiency Measurements

The first set of tests reveals the stability of the voltage rails and the PSU's efficiency. The applied load equals (approximately) 10 to 110 percent of the maximum load the supply can handle, in increments of 10 percentage points.

We conducted two additional tests. During the first, we stressed the two minor rails (5V and 3.3V) with a high load, while the load at +12V was only 0.10A. This test reveals whether a PSU is Haswell-ready or not. In the second test, we determined the maximum load the +12V rail could handle with minimal load on the minor rails.

Test12V5V3.3V5VSBPower(DC/AC)EfficiencyFan SpeedFan NoiseTemp(In/Out)PF/AC Volts
18.176A1.983A1.959A0.980A119.74W86.06%510 RPM21.1 dBA39.15°C0.979
12.010V5.033V3.365V5.078V139.13W44.48°C115.1V
217.370A2.980A2.948A1.182A239.38W90.00%565 RPM24.3 dBA40.30°C0.995
12.006V5.021V3.355V5.064V265.99W47.13°C115.1V
326.982A3.496A3.464A1.385A359.70W91.09%780 RPM30.1 dBA41.09°C0.996
11.993V5.012V3.347V5.049V394.89W48.17°C115.1V
436.587A3.994A3.952A1.585A479.47W91.31%1015 RPM33.9 dBA41.74°C0.997
11.980V5.003V3.338V5.036V525.10W49.07°C115.1V
545.872A5.007A4.955A1.789A599.36W91.18%1270 RPM42.1 dBA41.93°C0.998
11.966V4.990V3.328V5.020V657.35W49.49°C115.1V
655.168A6.026A5.968A1.995A719.14W90.49%1610 RPM43.7 dBA42.61°C0.998
11.952V4.978V3.317V5.004V794.69W50.55°C115.1V
764.499A7.040A6.983A2.201A839.03W89.98%1800 RPM46.4 dBA43.41°C0.998
11.938V4.967V3.307V4.988V932.48W53.09°C115.1V
873.857A8.075A8.008A2.411A959.07W89.28%1800 RPM46.4 dBA44.10°C0.998
11.924V4.955V3.296V4.973V1074.19W55.07°C115.1V
983.672A8.595A8.543A2.414A1079.03W88.60%1800 RPM46.4 dBA45.07°C0.998
11.909V4.945V3.288V4.967V1217.90W57.88°C115.1V
1093.246A9.120A9.057A3.035A1198.83W87.67%1800 RPM46.4 dBA47.27°C0.998
11.895V4.933V3.279V4.937V1367.51W61.41°C115.1V
11103.456A9.133A9.076A3.040A1318.74W86.81%1800 RPM46.4 dBA48.65°C0.998
11.880V4.927V3.272V4.930V1519.16W65.08°C115.2V
CL10.097A18.022A18.003A0.000A149.28W82.87%1640 RPM44.0 dBA44.83°C0.986
12.013V4.938V3.284V5.091V180.13W50.63°C115.2V
CL296.981A1.002A1.003A1.001A1202.15W88.12%1825 RPM46.5 dBA47.23°C0.998
12.257V5.012V3.346V5.074V1364.17W62.02°C115.5V

In the tough conditions that we conducted our tests in, the PSU didn't meet all the requirements of the 80 Plus Platinum certification. Actually, the unit managed to hit the target only with 20 percent load, which shows 90 percent efficiency. With 50 percent of its max-rated capacity load and with a full load, efficiency was significantly lower than the levels that the Platinum certification sets (92 percent and 89 percent, respectively). Nonetheless, in both cases the efficiency difference in the Platinum levels was within 1 percent, so we can give this PSU a pass, considering that ECOVA conducts their tests at only 23 C (73 F), while we conducted our tests at a much higher ambient temperature. As the operating temperature rises, the resistance of several components, including the FETs, increases leading to significant energy losses. On the other hand, the resistance of diodes, including components like SBRs (Schottky Barrier Diodes) and bridge rectifiers, actually lowers at higher temperatures. However, this PSU only uses FETs for the regulation of its outputs.

The Dark Power P11-1200’s load regulation performance wasn't able to meet its competition, although it was decent overall. In this price range the competition is fierce, offering very high performance. On the other hand, the be quiet! PSU delivered its full power more effortlessly than other unit, and at very high operating temperatures that were close to 49 C (120 F) during the 110 percent load test. Besides that, up to the 40 percent load test, the unit's noise was very low and in the worst-case scenario it didn't exceed 47 dBA. For a 1.2 kW PSU, the noise output is at very low levels, also given the tough conditions we applied during these tests.

  • Blueberries
    -12V Rail is very cool. These are really well built PSUs. I'd rather have a SeaSonic SS-1200 at this price range. I was expecting a better transient response change on the 5V rail, oh well.
    Reply
  • chalabam
    Interesting, but way too much focus on PSUs over the kW, when the system builder marathons had peak overclocked power at 750w (and mostly 500w) for years now.

    And those computers spend most of the time running at 50/100 w, where even this unit efficiency is poor.

    Good review, anyway, but I think that Tomshardware should focus on units that readers are more probable to buy. That info is more useful.
    Reply
  • chalabam
    16727117 said:
    -12V Rail is very cool. These are really well built PSUs. I'd rather have a SeaSonic SS-1200 at this price range. I was expecting a better transient response change on the 5V rail, oh well.

    Why you need 1200 W? What are you running?
    Reply
  • Blueberries
    16727128 said:
    16727117 said:
    -12V Rail is very cool. These are really well built PSUs. I'd rather have a SeaSonic SS-1200 at this price range. I was expecting a better transient response change on the 5V rail, oh well.

    Why you need 1200 W? What are you running?

    Just because it's rated for 1200W doesn't mean you're drawing 1200W from the wall. The PSU in the article is a 1200W PSU so it makes sense to compare the two.

    16727124 said:
    Interesting, but way too much focus on PSUs over the kW, when the system builder marathons had peak overclocked power at 750w (and mostly 500w) for years now.

    And those computers spend most of the time running at 50/100 w, where even this unit efficiency is poor.

    Good review, anyway, but I think that Tomshardware should focus on units that readers are more probable to buy. That info is more useful.

    Power supplies are more efficient and put off less heat when they're not near their maximum load. If your system draws 500W you don't want to use a 550W PSU, you would be straining the PSU. SLI/CrossFire builds with multiple graphic processors can achieve a power draw of over 750W on the PCI Express rails alone!

    I don't have a use for 1200W, but that wouldn't stop me from paying extra for better components, efficiency, and reduced noise.
    Reply
  • Aris_Mp
    indeed a PSU's peak efficiency is with typical loads (40-50% of its max rated capacity). However you should also take into account how long your system operates at full load. For example if your system is mostly working at idle or at low utilization then you will probably have more gain with a lower capacity PSU rather than with a high capacity one. On the other hand at high loads the stronger PSU will be closer to its sweet spot, having higher efficiency.
    Reply
  • Blueberries
    indeed a PSU's peak efficiency is with typical loads (40-50% of its max rated capacity). However you should also take into account how long your system operates at full load. For example if your system is mostly working at idle or at low utilization then you will probably have more gain with a lower capacity PSU rather than with a high capacity one. On the other hand at high loads the stronger PSU will be closer to its sweet spot, having higher efficiency.

    It is absolutely true that power supplies are usually at their best efficiency around 50% of their maximum load, but that doesn't necessarily mean a smaller PSU is better. An AX1500 can peak at ~94% 12V efficiency, which is really good, but even at 300W it's still producing 91% efficiency, and over 90% at 150W.
    Reply
  • Aris_Mp
    The AX1500i is a very special case :)
    Reply
  • Blueberries
    16732572 said:
    The AX1500i is a very special case :)

    Be that as it may it's important to look at all of the factors. Amperage, Ripple, Efficiency, Hold-up, etc. Most important of all of course is build integrity and architecture. The best PSUs do have high loads, because well, they can handle it. They'll also last longer at any load.

    An average load for an i7 user with a single high-powered video card is ~350W (gaming), a 980ti under maximum stress can be a 300-350W draw alone, bringing that up to a potential ~550W. In this scenario an RM750X is gold rated and will perform better than a Supernova P2 650W which is platinum rated. Both are extraordinary power supplies and I'd use either one. My point is, maximum load shouldn't matter. If a power supply meets more than your demands consider that a good thing. Most people aren't going to buy these PSUs unless they have a use for them because there's other options available.

    The Dark Power Pro 11 in this article retains >90% efficiency from 200W-800W, which is a wide range, and your system load would want to fall between that range to be in the "sweet spot." A smaller PSU has a much smaller "sweet spot," but it could prove to be better.
    Reply
  • mctylr
    indeed a PSU's peak efficiency is with typical loads (40-50% of its max rated capacity). However you should also take into account how long your system operates at full load.

    It is absolutely true that power supplies are usually at their best efficiency around 50% of their maximum load, but that doesn't necessarily mean a smaller PSU is better.

    All switching power supplies decrease their efficiencies as their load decreases, typically starting at or near 50% load and often rapidly decreasing efficiencies as their load falls below 20%.

    For desktop systems, unless you run a distributed computation project in the background, 80-95% of the time the system is powered on, the system is idle or near-idle. In my limited testing a desktop system likely draws 50-100W at idle, so with a 1000W power supply it's operating at 5-10% load, and thus at its worst efficiencies.

    With Haswell and newer consumer Intel's CPUs maxing out at 145W (I believe) at stock frequencies, and most video cards needing under 200-250 W maximum (980Ti 250W), a system with a single GPU rarely needs more then 600W.

    Specifying the PS for 50% load (for maximum efficiency) to match the maximum load the system is actually capable of drawing is a poor efficiency trade-off, as the system will spend the majority of time time at under 20% utilization, at its worst efficiency, that the few percentage points of increased efficiency (at 50% load versus moderately higher loads) will result in a net lost.

    Edited: Clarify first paragraph
    Reply
  • Blueberries
    16734708 said:
    indeed a PSU's peak efficiency is with typical loads (40-50% of its max rated capacity). However you should also take into account how long your system operates at full load.

    It is absolutely true that power supplies are usually at their best efficiency around 50% of their maximum load, but that doesn't necessarily mean a smaller PSU is better.

    All switching power supplies decrease their efficiencies as their load decreases, typically starting at or near 50% load and often rapidly decreasing efficiencies as their load falls below 20%.

    For desktop systems, unless you run a distributed computation project in the background, 80-95% of the time the system is powered on, the system is idle or near-idle. In my limited testing a desktop system likely draws 50-100W at idle, so with a 1000W power supply it's operating at 5-10% load, and thus at its worst efficiencies.

    With Haswell and newer consumer Intel's CPUs maxing out at 145W (I believe) at stock frequencies, and most video cards needing under 200-250 W maximum (980Ti 250W), a system with a single GPU rarely needs more then 600W.

    Specifying the PS for 50% load (for maximum efficiency) to match the maximum load the system is actually capable of drawing is a poor efficiency trade-off, as the system will spend the majority of time time at under 20% utilization, at its worst efficiency, that the few percentage points of increased efficiency (at 50% load versus moderately higher loads) will result in a net lost.

    Edited: Clarify first paragraph

    Yes but titanium efficiency PSUs retain 90% efficiency at a 10% load and platinum achieve at least 90% efficiency at 20% load. See: https://en.wikipedia.org/wiki/80_Plus

    If the components are good they'll be able to handle a large load. There's no such thing as a good PSU that can't handle a large load. Most platinum PSUs can handle well over what they're rated for.
    Reply