Power supplies might not steal the PC hardware spotlight, but their essential job remains unchanged: delivering stable, reliable power to your components by converting incoming AC into usable DC. High-end models excel at this, achieving high efficiency with minimal noise. This tradition is continued with the be quiet! Pure Power 13 M 850W, a PSU that strikes a fine balance between performance, silence, and advanced features, making it suitable for both enthusiasts and mainstream users.
be quiet! Pure Power 13 M 850W is certified 80 Plus Gold with a touted efficiency of over 94%. The most compelling benefit of this figure is lower power consumption, which leads to lower costs and, above all, cooler and quieter operation. This particular model aims to cater to users who want dependable power without the complexity or premium price tag of enthusiast-tier units such as Dark Power, making it a versatile choice in today’s competitive PSU market.
Building on solid foundations of its Pure Power 12 M predecessor, the 2025 range encompasses common capacities from 550W through to 1,000W and integrates advanced electrical architectures with user-friendly modular cabling, making it suitable for diverse PC builds from gaming to professional workstations. I feel as if its focus on low noise operation and compliance with current industry standards further highlights usefulness for demanding environments requiring both performance and tranquillity.
be quiet! Pure Power 13 M 850W
£109.99 / $134.90
Pros
- Very good overall performance
- High efficiency
- Excellent noise characteristics
- 10-year warranty
- ATX 3.1 and PCIe 5.1 compatibility
Cons
- No fan failure protection
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How we test and review products.
Furthermore, Pure Power 13 M series features full support for the ATX 3.1 and PCIe 5.1, which ensures compatibility with all wattage-heavy components, like the Nvidia GeForce RTX 4000/5000 series. This also means be quiet!’s PSU uses the latest 12V-2×6 (ATX12VO) power connector designed to deliver up to 600W of raw, unhindered power to the graphics card. You needn’t worry about the rather infamous 12VHPWR here.
When compared to ATX 2. X, which supports high load peaks but does not define a maximum above the nominal power of the power supply, ATX 3.1 represents clear target values – specifically, the PCIe connection for the graphics card must allow load changes of up to three times the power consumption. There is a surge tolerance of up to 235%, too. In short, specifications are very robust for a design that’s more mid-tier than absolutely cutting edge.
I mentioned available capacities earlier. Here’s a full list of variants you can choose from.
| Capacity | 12V-2×6 cable | PCIe 6+2 pin | USD price |
| 550W | 300W | 2x | $94.90 |
| 650W | 450W | 2x | $104.90 |
| 750W | 600W | 4x | $119.90 |
| 850W | 600W | 4x | $134.90 |
| 1,000W | 600W | 4x | $164.90 |
I’m happy with the wattage spectrum here. The 850W and 1,000W models, in particular, are solid for the setups with high-end CPUs like AMD Ryzen 9 series/Intel Core i7/i9 combined with the GPUs as powerful as AMD RX 9070 XT or Nvidia RTX 5080/5090. Along with the 750W model, they all have a 600W 12V-2×6 cable in situ.
Among notable features not mentioned thus far is the semi-fanless mode, utilisation of a half-bridge topology with DC-DC conversion, and a 10-year warranty. All good stuff.
Looking across to the competition, pricing is consistent with other models touting a similar feature-set. Here in the UK, for example, the review 850W is available for a little over £100, representing good value in my book.
Look and feel
The modular power supply is packaged in a typical black be quiet! cardboard box. On the front, you will find information about the model, PSU power, 80 PLUS and Cybenetics Gold certification, and a picture of the PSU. On the back, there is additional information about the current and voltage rating plate and a QR code that takes us to the product page. Also, there is also information about the PCIe 5.1 connector.
The power supply comes with the obligatory power cable, five long plastic ties, five screws for mounting purposes, and a user manual. There’s nothing superfluous here, which makes sense as be quiet! is targeting value as a key metric.
The cabling
The modular cabling includes a full set of essential connectors, from a standard 24-pin ATX to multiple PCIe connectors, SATA, and Molex, making it versatile enough for a range of builds from gaming rigs to workstations.
Graphics support is impressive, with a PCIe 5.1 12V-2×6 600W and 4 PCIe 6+2 connectors for overclocked, high-end models. This variety in connectors not only supports multiple GPU configurations but also allows for future expandability, which is a key consideration for users planning incremental upgrades.
Below, you can find a list of the supplied cables:
• 24-pin ATX cable (550 mm)
• 4+4-pin EPS cable (650 mm)
• 8-pin EPS cable (650 mm)
• 6+2-pin PCI-e cable (600 mm)
• 6+2-pin PCI-e cable (600 mm+150 mm)
• 12+4 PCIe (600 mm)
• Quad SATA cable (510+150+150+150 mm)
• Sata/Molex cable (510 mm SATA + 150 mm SATA + 150 mm Molex + 150 mm Molex)
be quiet! uses cables with a cross-section of 16 AWG and 18 AWG (American Wire Gauge, where a lower number means a larger cross-section). Additionally, its thoughtful design ensures that even smaller PC cases or builds with tight space constraints can accommodate it comfortably, enhancing its overall usability.
Detailed inspection
Dimensions are (W x H x D): 150 mm x 85 mm x 160mm, and the weight is 1.76 kg (3.88 lb). These are perfectly normal for a PSU of this ilk.
Pure Power 13 M 850W is a compact powerhouse with a modern, sleek design typical of be quiet! ‘s understated aesthetic. Its black matte finish and solid build quality exude reliability without flashy RGB distractions – perfect for those, like me, who value substance over style.
Equipped with a 120mm silent fan, the unit keeps noise levels impressively low with the fan only spinning up at higher loads, ensuring quiet operation during typical use. BQ QF2-12025-HS with a rifle bearing that operates in semi-passive mode. The maximum speed is 2000rpm, and the fan blades have been designed to optimise airflow, hence their corrugated shape.
The fan is covered by a tasteful black wire grille, which has been a typical design feature of be quiet! power supplies for several years. An interesting detail is that, in addition to the white brand logo on the fan, Pure Power 13 M model also features a silver ring around it.
Internals
As for the topology, it’s APFC, Half-Bridge & LLC Resonant Converter for the primary side, and for the secondary, it’s Synchronous Rectification for 12V & DC-DC converters for minor rails. I’ll translate this word spaghetti for you by saying the innards are high quality. The OEM for this PSU is FSP, who is a well-known and good manufacturer.
The APFC MOSFETs are 2x GP36S60YERD with Texas Instruments UCC28180 and Champion CM6500UNX APFC Controller. The resonant controller is Champion CM6901X. The main switchers are 2x ROHM Semiconductor R6035VNX3 (600V, 35A @ 25°C, Rds(on): 0.119Ohm)
Performance and efficiency
My first basic test is performed with a power supply tester. It doesn’t load the PSU with more than a couple of watts, but it helps determine whether the power supply unit is operational. A self-check indicates whether the voltages are at the proper levels. As you can see, there are no issues with the be quiet! Pure Power 13 M 850W unit.
The following professional setup was used for the remainder of the testing:
• Voltcraft VC-870 Digital Multimeter – voltage measurement
• Oscilloscope – GW INSTEK GDS 3154
• DC load – original solution
• Fluke 97 Scope meter (a measurement of voltage and ripple)
• Voltcraft SL-451 decibel meter (volume measurement)
• ACUVIM-IIRF is used to measure active power (input from the socket).
• PCE Instruments PCE-DT 50 tachometer – for the measurement of the rotational speed of the fan.
Measurements are taken only using 230 V input voltage.
I’ll give you the TLDR first. Pure Power 13 M 850W boasts 80 Plus Gold certification, delivering excellent efficiency that keeps power waste and heat generation in check. Under typical loads, the PSU consistently maintains high efficiency, beating many competitors in its class. This high efficiency directly translates into lower electricity bills for users running their systems extensively, as well as a reduced environmental impact.
Given the ability to run ATX12VO, Pure Power 13 M 850W houses a single 12V rail capable of delivering the full 70.9A down the wire. Should you need to use 5V and 3.3V, there’s 22A available on each, though not concurrently, of course.
12V regulation
| Wattage | be quiet! Pure Power 13 M 850W |
| 85W (10%) | 12.18V |
| 212W (25%) | 12.16V |
| 425W (50%) | 12.14V |
| 637W (75%) | 12.11V |
| 850W (100%) | 12.08V |
Voltage remains solid across the load spectrum, with minimal deviation from the ideal 12V rail output, providing stable power to sensitive components even at full load. This stability is crucial because voltage fluctuations can cause system crashes or hardware damage, especially in high-performance components like CPUs and GPUs.
Wide-load efficiency
| Wattage | be quiet! Pure Power 13 M 850W |
| 85W (10%) | 88.64 per cent |
| 212W (25%) | 92.71 per cent |
| 425W (50%) | 93.39 per cent |
| 637W (75%) | 92.52 per cent |
| 850W (100%) | 92.34 per cent |
80 Plus Gold PSUs are the optimal price/performance choice, in my opinion. Pure Power 13 M 850W is comfortably above 90% efficiency at workloads common on consumer PCs.
Low-load efficiency
| Wattage | be quiet! Pure Power 13 M 850W |
| 40W | 81.34 per cent |
| 60W | 86.67 per cent |
Examining low-load efficiency is equally important if, like us, your PC spends a vast amount of time idling. The wide-load efficiency range, however, ensures that whether your system is running basic tasks or pushing full CPU and GPU performance, the PSU operates economically, minimising heat output and potentially extending the lifespan of your computer’s components.
12V ripple suppression
| Wattage | be quiet! Pure Power 13 M 850W |
| 85W (10%) | 27.4mV |
| 212W (25%) | 26.5mV |
| 425W (50%) | 23.2mV |
| 637W (75%) | 24.3mV |
| 850W (100%) | 26.8mV |
Ripple is caused by converting mains AC to PSU DC, and having a low suppression figure is ideal. The unit exhibits relatively low ripple voltage on the 12V rail, which translates to cleaner power delivery, protecting components and enhancing system stability.
Reduced ripple contributes to better long-term health of your PC parts, too, and it can even lead to slightly improved overclocking headroom because delivered power is consistent and mostly free of electrical noise.
Noise
| Wattage | be quiet! Pure Power 13 M 850W |
| 85W (10%) | 30.0dBA (0 rpm) |
| 212W (25%) | 30.0dBA (0 rpm) |
| 425W (50%) | 31.2dBA (750 rpm) |
| 637W (75%) | 31.2dBA (750 rpm) |
| 850W (100%) | 31.5dBA (810 rpm) |
It’s a great result. The 120mm fan’s intelligent control keeps noise to a minimum, with the PSU practically silent during low to medium workloads. Even under heavy loads, the noise output remains subdued, making it an excellent choice for quiet PC builds. This cooling efficiency means the PSU can maintain stable operation without resorting to aggressive fan speeds, which often cause distracting noise spikes in less well-designed units.
The background noise in my lab is 30 dBA, so even under a full load I can barely hear the fan which spins at around 800rpm at full chat.
Conclusion
be quiet!’s Pure Power 13 M 850W stands out as a well-rounded PSU that combines reliable, efficient power delivery with quiet operation and flexible modular cabling. Its 80 Plus Gold efficiency rating assures low energy waste, while the sturdy build and solid protections give peace of mind for both gamers and professionals.
Though not the highest wattage, 850W is ample for many modern builds, and its compact size and silent fan make it especially appealing for those prioritising quiet and efficient systems. For users who want a balance of quality and value without unnecessary bells and whistles, this power supply is a compelling choice that should meet the needs of a wide variety of applications.
I like that be quiet! uses semi-passive cooling, and the 120mm fan only starts at around 50% load. In return, you get one of the quietest power supplies in its class, which even under full load maintains a fan speed of around 800rpm. The average efficiency in the 20–100% range is close to 93% and the maximum efficiency is 93.39% at 50% load. This is very close to 80 Plus Platinum standards.
In addition, Pure Power 13 M 850W features modular cabling with 16 AWG wires on the CPU and PCIe lines and a full set of safety features. The manufacturer also offers a 10-year warranty, which further confirms the quality of the components and workmanship.
The be quiet! Pure Power 13 M 850W stands out with an eye toward future system compatibility and a commitment to build quality. This PSU is a future-proof investment that caters to both current high-performance builds and evolving hardware requirements, making it an attractive option for discerning PC builders and system integrators.
Verdict: The combination of clean power delivery, flexible cabling, and near-silent operation makes the be quiet! Pure Power 13 M 850W PSU suitable for users aiming to create a performant yet unobtrusive PC environment.
