be quiet! Pure Power 11 FM 550W

Be quiet! Pure Power 11 FM 550W

The best low-capacity PSU in 2022.

(Image: © Future)

Our Verdict

With the right price, this product can cause headaches to Corsair and EVGA in the mid to high-end 550W region.


  • High performance
  • Silent operation
  • Compatible with the Alternative Sleep Mode
  • Good build quality


  • Only two 4-pin Molex connectors

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Be quiet! developed a unique platform along with Channel Well Technology for its Pure Power 11 FM line, and the results are fantastic. The Pure Power 11 FM with 550W capacity is our top choice for this wattage category, hence why it's one of the best power supplies for gaming, and it is ideal for not demanding systems where users require a top-quality PSU under $100.


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Manufacturer (OEM)Channel Well Technology
Max. DC Output550W
Efficiency80 PLUS Gold, Cybenetics Gold (87-89%)
NoiseCybenetics A (20-25 dB[A])
ModularYes (fully)
Intel C6/C7 Power State SupportYes
Operating Temperature (Continuous Full Load)0 - 40°C
ProtectionsOVP, UVP, OPP, OCP, OTP, SCP, surge
No Load OperationNo
Cooling120mm Rifle Bearing Fan (BQ QF2-12025-MS)
Semi-Passive OperationNo
Dimensions (W x H x D)150 x 85 x 160mm
Weight1.56 kg (3.44 lb)
Form FactorATX12V v2.52, EPS 2.92
Warranty5 Years

The PSU is 80 PLUS Gold and Cybenetics Gold certified in efficiency and has a Cybenetics A noise rating, proving it is quiet. The dimensions are standard, with 160mm depth, and the cooling fan uses a rifle bearing for increased reliability. The five-year warranty is half than what the competition provides (e.g., the Corsair, RM550x). Still, you cannot call it short.

The CWT platform has good soldering quality in general. Our main objection is the 85C bulk caps when the competition uses 105C caps. The Elite caps on the secondary side are the best alternatives to Japanese caps, which are hard to find nowadays and super expensive. Lastly, the low speed uses a rifle bearing, so it won’t have a problem outliving the warranty (and even more).

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Max. Power (amps)2020282430.3
Max. Power (watts)120120550550153.6

There are two 12V rails that can deliver up to 550W combined, while the minor rails can go up to 120W. The standby rail is also strong enough, with 3A max current output.

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CableAmount includedIn-cable caps
ATX Connector 20+4 pin1No
4+4 pin EPS12V1No
6+2 pin PCIe2No
SATA / 4-pin Molex / FDD1No
AC Power Cord1N/A

The ATX cable could be a bit longer. The same applies to the single EPS cable. It would also be nice to have one EPS and one ATX12V connector instead of a single EPS. The two PCIe connectors are on dedicated cables, so everything is fine there, the distance between all peripheral connectors is adequate, and the FDD connector could be replaced with a 4-pin Molex to increase their number to three.


The load regulation at 12V is satisfactory and tight on the other rails, and ripple suppression is excellent!

The hold-up time is notably longer than 17ms, which is what the ATX spec requires, and the power ok signal’s hold-up time is close to 16ms. The inrush current is low with 115V, and on the high side with 230V.

It must be said this is a highly efficient platform: The 5VSB rail has decent efficiency, and vampire power is low. The average efficiency is high, even for a Gold rated unit.

The transient response voltage deviations are kept low on all rails, and the PWR_OK delay is within the 100-150ms region, so the PSU supports the alternative low power modes recommended by the ATX spec.

The OCP triggering point on the first 12V rail is high and sky-high on the second one. Having highly set OCP is logical in low capacity PSUs to avoid issues with power spikes, given that the platform can handle such high power loads. The over power protection, on the other hand, is conservatively set. In general, it is not ideal to overstress your power supply. If you need more power, get a stronger PSU.

As for noise, the Be quiet! unit honors the name of its brand, remaining quiet, but the Corsair RM550x (2021) is even better here. 

Final thoughts

be quiet! Pure Power 11 FM 550W

(Image credit: Future)

Be quiet! has a long history in making silent products and power supplies, among others. This brand might not be so popular in the US market, which is among the key players, but it is trendy in Germany, its country of origin and with products like the Pure Power 11 FM 550, it won’t be hard to gain worldwide popularity, soon.

The Pure Power 11 FM 550 showed that it has no problem facing intense competition from Corsair, Seasonic, EVGA, Cooler Master, and others. Perhaps its best competition is the Seasonic Focus Plus Platinum 550W, but this is still the outright winner.

The Verdict
Be quiet! Pure Power 11 FM 550W

With the right price, this product can cause headaches to Corsair and EVGA in the mid to high-end 550W region.