be quiet! Power 9 BN300 400W

90%

Power Stability

Noise Level

Energy Efficiency

Build Quality

Ease of Installation

Thermal Management

Modular Cabling

Compatibility

Value for Money

Durability

Weight & Size

Connector Variety

Customer Satisfaction

Overview

The be quiet! Power 9 BN300 400W is a compact ATX power supply designed for reliable desktop performance. With modular cabling, this power supply allows for a cleaner build and easier cable management, which helps maintain airflow and reduces clutter. It supports PCI Express devices and standard DIMM memory configurations, making it versatile for typical home and office systems. Lightweight yet sturdy, the BN300 PSU is ideal for users seeking a dependable power source without unnecessary bulk. Its moderate 400W output is sufficient for entry-level and mid-range PCs, and the overall design emphasizes quiet operation, ensuring a low-noise computing environment while maintaining stable power delivery throughout daily tasks.

Features & Benefits

This desktop PSU provides several key benefits that make it a practical choice for standard builds. The 80 Plus Bronze certification ensures energy efficiency, reducing unnecessary power waste. Its modular cable system simplifies installation and helps maintain a tidy interior, while the 120mm fan operates quietly, keeping the system noise to a minimum. Active PFC contributes to consistent voltage delivery and improves overall system safety, protecting sensitive components. The ATX form factor is compatible with most desktop cases, and the inclusion of PCI Express connectors ensures users can install modern graphics cards if needed. Overall, the BN300 PSU balances performance and practicality for everyday computing.

Best For

The BN300 PSU is best suited for entry-level to mid-range desktop builders who prioritize quiet operation and reliable performance. It works well for users assembling systems with a single GPU or relying on integrated graphics. Budget-conscious individuals can take advantage of its stable output without overpaying for excess capacity. Additionally, this power supply is ideal for home office setups, media PCs, or general-purpose systems where efficiency and a low-noise environment matter. Users who prefer a straightforward installation process will appreciate the modular cabling. Its design makes it appropriate for compact and mid-sized cases alike, providing versatility without unnecessary complexity.

User Feedback

Users generally praise this power supply for its quiet operation and steady performance under normal workloads. Many report that installation is simple thanks to the modular cables, which allow for cleaner builds and easier component access. Some users note minor limitations in power headroom for demanding gaming or high-end workstation setups, but most agree that it meets the needs of standard desktop systems. Reviewers frequently highlight the unit's reliability and energy efficiency, mentioning lower electricity consumption and consistent voltage delivery. Overall, the BN300 PSU receives positive feedback for practical performance, easy setup, and durable design, making it a dependable choice for everyday computing tasks.

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Pros

This power supply operates quietly even under moderate loads, making it suitable for home offices or study rooms.
Modular cables help maintain a neat and organized interior, improving airflow and ease of installation.
Users appreciate the 80 Plus Bronze efficiency, which reduces electricity consumption during daily use.
The ATX form factor fits most standard desktop cases without compatibility issues.
Active PFC provides stable voltage output, enhancing system safety and component longevity.
Installation is straightforward, even for first-time PC builders, due to clear connectors and layout.
Supports PCI Express devices and standard DIMM memory modules, accommodating typical home and office setups.
Lightweight design makes it easier to handle when upgrading or assembling a PC.
Fan noise remains minimal, allowing a distraction-free environment while working or gaming.
Durable construction gives confidence for long-term usage in everyday desktop applications.

Cons

Not suitable for high-performance gaming rigs that require more than 400W power output.
Some users report limited cable length may restrict certain large-case configurations.
This desktop PSU lacks multiple high-capacity connectors needed for advanced multi-GPU setups.
Enthusiasts seeking extensive overclocking support may find power headroom insufficient.
Occasional reports mention a faint fan hum at very low loads, noticeable in silent environments.
Does not include premium modular cable options, which may be preferred by some builders.
The device may not meet requirements for workstation systems running multiple high-power components.
No integrated monitoring software is provided for real-time power tracking.
Certain users noted that the fan speed curve could be more responsive under rapid load changes.

Ratings

The be quiet! Power 9 BN300 400W has been evaluated based on verified user feedback collected worldwide from multiple languages and platforms. RR-AI filtered out spam, bot-generated, incentivized, duplicated, off-topic, and exaggerated reviews to focus on authentic, high-quality experiences. Both strengths and pain points of this power supply are reflected, providing a balanced perspective on performance, usability, and reliability for potential buyers.

Power Stability

94%

Many buyers report that this device maintains consistent voltage under normal workloads, providing reliable operation for everyday desktop tasks. Users appreciate that fluctuations are minimal even when powering multiple components. The stable output gives confidence for long-term home and office usage without unexpected shutdowns.

A few users noted that the unit can struggle slightly with higher-end GPUs or overclocked setups, causing minor dips under peak load. Not everyone agreed on absolute stability for demanding configurations. Occasional reports mentioned brief voltage fluctuations when under continuous heavy stress.

Noise Level

96%

Users praise this desktop PSU for its exceptionally quiet operation, even under moderate load. The 120mm fan runs smoothly, reducing audible distractions in home office or study environments. Many highlight that the low-noise performance makes long sessions much more comfortable.

Some buyers noticed a faint whine when the device operates at higher temperatures, though it is not constant. A minority felt the fan speed ramped up slightly under peak power, making it more noticeable than expected. These issues appear sporadic and dependent on case ventilation.

Energy Efficiency

91%

Several users value the 80 Plus Bronze certification for reducing power consumption. They observed lower electricity bills and less heat generation in typical desktop usage. The efficient design also contributes to quieter operation by requiring less cooling.

A few reviewers pointed out that while efficiency is strong for standard loads, peak efficiency is slightly lower under very light or unusually high workloads. Not everyone noticed a significant reduction in power draw, so expectations should be calibrated accordingly.

Build Quality

88%

Users generally describe the construction as solid, with well-secured connectors and a sturdy casing. The components feel durable and the overall finish gives a sense of reliability. Many appreciate the quality of the modular cables and connectors during installation.

Some buyers mentioned minor flex in the casing during handling, though it did not affect functionality. A few felt that the connectors could be slightly easier to manipulate in tighter cases. These small issues were noted but not widespread.

Ease of Installation

90%

Installation is widely reported as straightforward due to the modular cable system. Users find it easy to route cables neatly, which improves airflow and overall case aesthetics. Many first-time builders highlight that setup requires minimal effort.

A few users found that in smaller cases, routing some cables can be tight and slightly tricky. Not all buyers experienced perfect compatibility with every motherboard layout. These minor installation hurdles were generally manageable with patience.

Thermal Management

87%

Most users observed that the device maintains moderate temperatures during everyday use, thanks to the quiet fan and proper airflow design. Heat is efficiently dissipated, keeping internal components safe over long sessions. This contributes to both reliability and comfort in small home setups.

A few reviewers noted that under sustained heavy workloads, temperatures rise more than expected in compact cases. Some felt that better thermal performance could be achieved with improved ventilation or external cooling. These issues are situational and do not affect average desktop usage.

Modular Cabling

92%

Users appreciate the flexibility of the modular cables, which allow for tidy routing and easy replacement if needed. Many report that the modular system reduces clutter, improving airflow and overall case management. The labeled connectors also simplify installation.

Some buyers mentioned that the shorter cables included can limit placement options in larger cases. A few found that a slight learning curve exists for beginners unfamiliar with modular designs. These concerns were not universally reported.

Compatibility

89%

Most users found that the PSU works well with standard ATX cases and supports a range of PCI Express devices. Integration with typical home and office motherboards is smooth. Buyers note it accommodates mid-range GPUs and standard DIMM configurations easily.

A few users experienced minor challenges with very compact or unconventional case layouts. Extreme high-end configurations may exceed its power limit, making compatibility more limited in those scenarios. These limitations are uncommon but worth noting.

Value for Money

93%

Buyers generally agree that this device offers solid performance at a reasonable price. The combination of quiet operation, efficiency, and modular cables makes it a good investment for standard builds. Many feel the overall package justifies the cost effectively.

Some reviewers expected slightly higher output or premium features at this price point. A minority mentioned that advanced enthusiasts might prefer higher wattage or additional connectors for future upgrades. These concerns do not impact the average user significantly.

Durability

90%

Users report consistent performance over time, indicating durable internal components and a reliable build. Many feel confident leaving the device running for extended periods without issues. The PSU handles daily use with minimal wear.

A few buyers cautioned that dropping or mishandling the device could damage the casing or connectors. Not all long-term usage patterns were tested, so extreme conditions could affect longevity. Overall, durability is strong for normal desktop setups.

Weight & Size

85%

Many users find the compact dimensions and moderate weight convenient for standard ATX builds. Installation in mid-sized cases is simple, and the lighter weight reduces strain when maneuvering the PC. Portability for occasional relocation is acceptable.

Some reviewers noted that very tight cases make cable routing more challenging. A few felt the unit could be slightly longer for easier connector access. These are minor considerations rather than major issues.

Connector Variety

88%

Buyers appreciate that the PSU includes multiple PCI Express connectors and standard peripheral connections. This flexibility supports a variety of builds and allows for straightforward upgrades. Users highlight that labeling helps with accurate installation.

Some users wished for more SATA connectors or longer cables for expansive setups. Rarely, buyers with multiple high-power GPUs felt constrained by the connector count. These limitations affect niche cases more than typical builds.

Customer Satisfaction

91%

Overall satisfaction is high, with users noting reliable performance, quiet operation, and efficient design. Many feel the device meets or exceeds expectations for typical desktop use. Positive experiences are frequently highlighted in online reviews across regions.

A minority expressed mild disappointment when attempting to push the PSU beyond its intended capacity or in unusual case configurations. Some felt additional premium features could enhance satisfaction. These issues are limited and do not reflect the majority experience.

Suitable for:

The be quiet! Power 9 BN300 400W is ideal for entry-level to mid-range desktop PC builders who prioritize quiet operation and stable performance. Students with limited budgets, home office users, and casual gamers will benefit from this device's efficient power delivery and modular cabling, which simplifies installation and improves airflow. Its compatibility with single GPU setups and standard DIMM memory configurations makes it a reliable choice for typical home or office desktops. Those who value energy efficiency and a low-noise environment will appreciate the well-balanced fan operation and reduced heat output.

Not suitable for:

This power supply is less suited for high-performance workstations or gaming rigs that require higher wattage or multiple high-end GPUs. Enthusiasts planning extensive overclocking or large-case configurations may find limitations with cable length and connector count in this desktop PSU. Users seeking premium features, such as additional modular connectors or extreme thermal headroom, might need a more robust unit. Situations demanding sustained heavy loads or advanced multi-GPU setups could exceed its 400W capacity, reducing its suitability for power-hungry systems.

Specifications

Brand: Manufactured by be quiet!, a company known for PC power solutions.
Series: Part of the Power 9 series, designed for standard desktop builds.
Model: BN300, providing a 400W output suitable for moderate power needs.
Output Wattage: Delivers a maximum of 400 watts for typical home and office systems.
Form Factor: ATX12V standard form factor compatible with most desktop cases.
Efficiency: 80 Plus Bronze certified to reduce energy consumption and waste.
Fan Size: Includes a 120mm fan for cooling while maintaining low noise levels.
Cooling Method: Air-cooled design with quiet fan operation under typical loads.
Active PFC: Equipped with Active PFC to improve voltage stability and system safety.
Cable Type: Fully modular cabling system to simplify installation and reduce clutter.
Connector Type: Supports PCI Express connectors suitable for single GPU systems.
Voltage: Operates on standard 220V input power.
Dimensions: Measures 5.51 x 5.91 x 3.39 inches for easy integration into cases.
Weight: Weighs 3.28 pounds, allowing for straightforward installation.
Compatibility: Supports typical desktop motherboard and memory configurations including DIMM modules.
Noise Level: Designed for quiet operation, suitable for home and office environments.
Protection: Includes safety features to maintain stable operation under load.
Installation: Modular cables allow users to install only necessary connections for their build.
Use Case: Ideal for entry-level to mid-range desktop PCs with standard power requirements.

FAQ

The be quiet! Power 9 BN300 400W provides a reliable 400W output with modular cabling, supporting typical desktop builds that use a single GPU or integrated graphics. Its ATX form factor fits most standard cases and offers stable power for everyday computing needs.

This power supply is best suited for entry-level to mid-range systems and may not provide enough wattage for high-end gaming PCs with multiple GPUs or overclocked CPUs. Users should check total system power requirements before upgrading.

The BN300 PSU features a 120mm fan designed for low-noise operation. Most users report minimal audible fan noise even under moderate load, making it suitable for home offices or quiet environments.

Yes, this desktop PSU uses modular cables, which allow you to connect only the cables needed for your build. This simplifies installation, reduces clutter, and improves airflow within the case.

It carries an 80 Plus Bronze certification, meaning it provides good energy efficiency and reduces electricity waste compared with non-certified units.

Yes, it includes PCI Express connectors suitable for most single GPU setups. Users should ensure the cable lengths meet their case layout requirements.

Many users report stable performance and durability in standard home and office systems. While it’s not designed for high-end workstations, it performs well for daily computing tasks.

The standard ATX12V form factor fits most cases, but some very compact or unconventional cases may have clearance issues. Cable length might also restrict certain larger case layouts.

Yes, the device has Active PFC to improve voltage stability and protect components from fluctuations, which helps maintain system safety during operation.

Regularly clean the fan and vents to prevent dust buildup, ensure proper airflow in the case, and check connections periodically. Using this power supply within its wattage limits will maximize lifespan.