be quiet! Straight Power 11 Platinum 1200W Quiet Performance Power Supply | Fully Modular | BN645
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AI Verdict
The Straight Power 11 Platinum 1200W is a dead-silent, multi-rail powerhouse for high-end rigs, but its five-year warranty and lack of native ATX 3.0 support show its 2020 age.
It delivers top-tier electrical performance and unmatched silence for heavy workstations. The older ATX 2.0 spec, reliance on daisy-chained PCIe cables, and short 5-year warranty make it a tough sell for modern RTX 4090 gaming builds compared to newer ATX 3.0 units.
If you are building a new rig with an RTX 4080 or 4090, look for an ATX 3.0 power supply with native 12VHPWR support.
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Pros
- Hits 93.9% efficiency at 50% load, easily clearing 80 PLUS Platinum standards
- 135mm Silent Wings 3 fan stays virtually inaudible even when pushing 1000W+
- Wire-free internal DC side improves airflow and reduces heat buildup
- Multi-rail design with four independent 12V rails provides excellent voltage stability
Cons
- 5-year warranty falls drastically short of the 10-year standard set by competing flagship PSUs
- Only features three PCIe ports on the PSU side, forcing you to use daisy-chained cables for 4-pin GPUs
- Measures 170mm long, which makes cable routing tight in compact mid-tower cases
- Lacks a native 12VHPWR cable out of the box for RTX 40-series cards
Dimension Scores
Consistently hits 93.9% Platinum efficiency with rock-solid voltage regulation across its four 12V rails.
The 135mm Silent Wings 3 fan makes this one of the quietest 1200W units ever tested.
Internal wire-free design is brilliant, but the 5-year warranty knocks it down a peg compared to 10-year rivals.
The cables are thick, the 170mm unit length eats up space, and the 3-port PCIe layout is frustrating for 4-plug GPUs.
Best For
- Multi-GPU workstations or heavy rendering rigs that need sustained, quiet 1000W+ delivery
- Audio production PCs where power supply fan noise ruins recordings
- Large full-tower builds that can easily accommodate the 170mm length
Not Recommended For
- RTX 4090 owners who want four dedicated PCIe cables instead of relying on daisy chains
- Small form factor or compact mid-tower builds with limited PSU shroud clearance
Watch Out For
- Only three PCIe ports on the unit: If your GPU requires four 8-pin connectors, you are forced to use at least one daisy-chained pigtail cable.
- 5-year warranty limit: For a flagship 1200W unit, this is half the lifespan guarantee of standard 10-year warranties in this class.
- No native ATX 3.0 / PCIe 5.0 cable: You have to buy be quiet!'s separate 12VHPWR adapter cable or use the bulky Nvidia dongle for RTX 40-series cards.
- 170mm chassis length: It will physically fit in most ATX cases, but leaves very little room to bend the thick modular cables in the basement of compact cases.
Full Specifications
| ASIN | B085WW7B74 |
| Brand | be quiet! |
| Color | Black |
| Series | straight power 11 |
| Wattage | 1200 watts |
| Model Name | straight power 11 |
| Form Factor | ATX |
| Item Weight | 8.1 pounds |
| Manufacturer | be quiet! |
| Connector Type | PCI Express |
| Cooling Method | Air |
| Output Wattage | 1200 Watts |
| Item model number | BN645 |
| Compatible Devices | Personal Computer |
| Product Dimensions | 13 x 9.75 x 4 inches |
| Power Supply Design | Full Modular |
| Item Dimensions LxWxH | 13 x 9.75 x 4 inches |
| Item dimensions L x W x H | 13 x 9.75 x 4 inches |
What Buyers Say
The acoustic performance is the star of the show here, with almost every buyer praising how the 135mm fan stays dead silent even during heavy rendering workloads. The cable layout causes major headaches for modern GPU owners. Buyers frequently complain about the PSU only having three physical PCIe ports, forcing the use of ugly daisy-chained pigtails for power-hungry cards. The 170mm length catches many mid-tower builders off guard, requiring them to remove hard drive cages just to fit the stiff modular cables.
“Dead silent and handles my heavily overclocked rig without breaking a sweat, but only giving me 3 PCIe ports on a 1200W unit so I have to use ugly pigtail cables is a massive oversight.”
Common Praise
- 135mm fan is completely inaudible even when pulling 1000W+ from the wall
- Zero coil whine reported across the vast majority of units
- Platinum efficiency noticeably reduces heat output into the PC case
- Matte black finish and wire-free internal design look clean in open-shroud cases
Common Complaints
- 5-year warranty feels like a slap in the face for a flagship 1200W PSU
- Only 3 PCIe ports on the PSU means you must use daisy-chained cables for 4-pin GPUs
- 170mm length makes cable routing a nightmare in compact ATX cases
- Cables are stiff and difficult to bend in tight spaces
Ownership Tips
- You must read the manual to properly balance your GPU cables across the specific 12V rails (12V3 and 12V4) or you will trip the OCP and shut down your PC.
- The lack of a zero-RPM fan mode doesn't matter because the fan spins so slowly at idle you can't hear it anyway.
- Dust buildup is minimal thanks to the funnel-shaped fan intake design.
Frequently Asked Questions
Can this power an RTX 4090 if it only has three PCIe slots on the PSU?
Yes, but you have to use the included daisy-chained cables. The PSU rails can handle the wattage, but many builders prefer four separate cables for peace of mind.
Does it come with the 12VHPWR cable for Nvidia 40-series cards?
No, it only includes standard 6+2 pin PCIe cables. You will need to use the adapter dongle that came with your GPU or buy a compatible 12VHPWR cable directly from be quiet!.
How loud does the fan get under full load?
It stays incredibly quiet. The 135mm Silent Wings 3 fan rarely spins up fast enough to be heard over your case fans, even when pulling 1000W.
Is this a single-rail or multi-rail power supply?
It is a multi-rail PSU featuring four independent 12V rails. You need to balance your CPU and GPU cables across the rails according to the manual to avoid tripping the over-current protection.
Will this fit in a standard mid-tower case?
It depends on your hard drive cage. At 170mm long, it takes up a lot of space, leaving less room to route the stiff modular cables.
Buying Guide
When you buy a 1200W power supply, you are paying for massive headroom and silence, not just raw wattage. This specific unit uses a multi-rail design, meaning the power is split into four separate lanes rather than one giant pool. You have to plug your cables into the correct ports on the back of the unit to balance the load, otherwise your PC will shut off during heavy gaming. Keep in mind this is an older ATX 2.0 design, so it lacks the modern 16-pin cable required by the newest Nvidia graphics cards.
80 PLUS Platinum
This means the power supply converts at least 92% of the power from your wall into usable PC power, wasting very little as heat. Think of it like a highly fuel-efficient car engine.
Multi-Rail Design
It splits the 12V power into four separate circuits with their own safety limits. It's like having four separate circuit breakers in your house instead of one massive one, providing better safety but requiring careful cable placement.
170mm Length
Standard power supplies are usually 140mm to 150mm long. This extra length means it will eat into the cable-stashing space in the bottom of your PC case.
Alternatives
If you are building a modern system with an RTX 4080 or 4090, look for an ATX 3.0 or ATX 3.1 power supply with a native 12VHPWR cable and a 10-year warranty.
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