In the realm of high-performance computing, power supplies are critical, not just for stability but also for managing thermals and noise. Fanless power supplies, once limited in power output and efficiency, have emerged as an impressive feat of engineering, combining cutting-edge thermal solutions with extreme efficiency. These units are designed for enthusiasts who demand absolute silence without compromising performance or reliability.

Modern fanless PSUs rely on advanced passive cooling mechanisms—large heat sinks, innovative case designs, and often custom components—to dissipate heat effectively. Achieving such thermal performance without active cooling also necessitates ultra-high efficiency, typically Platinum or Titanium certified, to minimize wasted energy that would otherwise generate excess heat.

Beyond cooling, these power supplies often showcase state-of-the-art electrical engineering, from low-loss MOSFETs to advanced multi-rail designs and digital monitoring systems. Such innovations not only enhance performance but also provide precise control and insights into system power usage.

In this article, we delve into some of the best passively cooled PSUs we’ve tested and used in our builds. We highlight their unique design choices, efficiency metrics, and user-focused features.

Seasonic PRIME Fanless PX-500

The Seasonic PRIME Fanless PX-500 is a standout in the realm of passively cooled power supplies, combining excellent efficiency with a thoughtful, modular design. The model targets enthusiasts who demand absolute silence and premium build quality. Seasonic’s reputation in the PSU market, backed by a 12-year warranty for this model, positions the PRIME Fanless PX-500 as our top pic for 500 Watt fanless PSUs.

Build Quality and Design

As a fully passive power supply, the PX-500 eliminates the need for a fan, relying entirely on its perforated aluminum housing for heat dissipation. This isn’t just an aesthetic choice; the design ensures sufficient airflow for cooling, even in tightly packed cases. The open structure reveals the internal components, which might divide opinions. In a cleanly managed build, the exposed internals add an industrial charm, but in cases with tempered glass panels, it could clash with more minimalist designs.

The PSU’s modular design is another strong point. Seasonic provides a full suite of cables, including:

• A 24-pin ATX motherboard cable.
• Two 4+4 pin CPU cables.
• Two 6+2 pin PCIe connectors for GPUs.
• A mix of SATA and Molex cables for peripherals.

Cable lengths are generous, accommodating a range of case layouts, and the modularity simplifies installation, helping maintain clean airflow. The package even includes spare cable ties and a protective storage pouch for the PSU, highlighting the attention to detail in this premium product.

Performance and Efficiency

What truly sets the PRIME Fanless PX-500 apart is its 80 Plus Platinum certification, which guarantees at least 94% efficiency at 50% load. This means less wasted energy and lower heat output, both critical for a fanless unit. Seasonic’s engineering ensures excellent voltage regulation as well, with deviations limited to ±1% on the 3.3V and 12V rails—far exceeding the industry standard of ±5%.

The single-rail 12V design delivers up to 41A, making it suitable for systems with power-hungry GPUs and CPUs. While 500W might not sound like much in an era of multi-GPU setups and extreme overclocking, it’s more than adequate for modern single-GPU builds and power-efficient processors.

Installation and Usability

Installing the PX-500 is a straightforward affair, thanks to its standard dimensions and modular design. Seasonic recommends positioning the PSU with the perforated side facing upwards, allowing hot air to escape naturally—a logical setup for systems with adequate airflow. For cases with restrictive airflow, ensuring a clear path for cool air intake is critical to maintain safe operating temperatures

The modular cables simplify cable management, and Seasonic users will appreciate that this PSU is compatible with the existing modular cable layouts from other models in the PRIME series. This makes it easy to upgrade without having to reroute cables through your build.

Seasonic PRIME Fanless TX-600

The Seasonic PRIME Fanless TX-600 is a high-performance, fanless PSU designed for silent operation and premium efficiency. Boasting an 80 Plus Titanium certification and a 12-year warranty, it positions itself as an ideal choice for users prioritizing a noise-free experience without sacrificing power delivery.

Design and Build Quality

Seasonic has created a PSU that impresses both in performance and design. Its perforated honeycomb casing optimizes passive cooling, enabling efficient heat dissipation even under demanding conditions. This fanless unit operates in total silence, save for a faint static sound detectable only when the ear is directly placed against it—underscoring its credentials as a truly silent PSU.

The fully modular design is a highlight, allowing users to connect only the cables they need. Seasonic provides a set of flat black cables, which are both aesthetically pleasing and functional for airflow and cable management. The main 24-pin cable includes sleeving for added durability, although the absence of a 12-pin connector for high-end GPUs like Nvidia’s RTX 4000 series is a minor limitation.

Performance and Efficiency

The PRIME Fanless TX-600 doesn’t just promise silence—it delivers exceptional efficiency. With an 80 Plus Titanium certification, it achieves around 93% efficiency at high loads during testing and maintains excellent voltage stability. This means minimal wasted energy, lower heat output, and reduced electricity costs over time.

Our test system, which included an Intel i7-13700KF, a Z690 motherboard, and a GeForce RTX 3080, pushed the PSU close to its 600W limit. Despite this, the PSU held steady, with temperatures peaking at just 21.3°C. This is a testament to the effectiveness of its passive cooling design. At lower loads (~350W), efficiency climbed even higher, emphasizing the unit’s suitability for quieter, mid-range systems.

Technical Specifications

The TX-600 adheres to top-tier standards, including protections such as OPP, OVP, UVP, OCP, OTP, SCP, and compliance with safety certifications like cTUVus, TUV, and CE. It is rated for continuous operation at temperatures up to 45°C, with a linear derating starting at 40°C. The unit delivers a maximum of 50A on the +12V rail, providing stable power for CPUs and GPUs alike.

Installation and Usability

Installing the PRIME Fanless TX-600 is straightforward. Its standard ATX form factor fits most cases, and the modular design ensures flexibility during assembly. For optimal performance, Seasonic recommends mounting the PSU with its perforated side facing upwards, allowing warm air to escape naturally.

The provided cables are of varying lengths to accommodate different case layouts, and the inclusion of Velcro ties and a branded storage pouch is a nice touch for cable organization. However, the packaging uses excessive single-use plastic, which feels out of place in an otherwise premium product.

SilverStone Nightjar NJ700 PSU

Design and Build Quality

The SilverStone Nightjar NJ700 is a passively cooled PSU with an impressive 700W output, boasting an 80Plus Titanium certification for top-tier efficiency. Its perforated chassis design maximizes passive airflow, while its 170 mm length makes it slightly larger than standard ATX units. The modular design offers flexibility with all-black cables, including ribbon-like connectors for easy routing. This unit’s build quality is exceptional, featuring premium Japanese capacitors and a sturdy design tailored for silent, high-performance systems. However, users must ensure adequate case ventilation to prevent heat buildup.

Performance and Efficiency

The NJ700 delivers remarkable efficiency, maintaining a 95% average under typical loads with peak efficiency exceeding 96%. Even in high ambient temperatures, it demonstrates resilience, with efficiency dropping only by 0.25%. Voltage regulation is excellent, with minimal ripple across all rails—just 12 mV on the 12V line under full load. Its performance rivals or surpasses actively cooled PSUs, maintaining stability and efficiency despite the absence of a fan. However, the heat generated will be dissipated within the case, requiring additional consideration for system cooling.

Technical Specifications

The NJ700 is powered by a robust platform developed by SeaSonic, a leader in PSU design. Internally, it features a full-bridge topology with an LLC resonant converter and advanced MOSFETs to enhance efficiency and reliability. Key components include high-grade Nippon Chemi-Con and Rubycon capacitors, ensuring durability and performance. Connectivity is versatile, offering a fully modular interface with multiple PCI-E, SATA, and Molex connections, making it suitable for modern gaming or workstation builds.

Installation and Usability

The modular cable design simplifies installation, while the dual mounting options for the PSU’s orientation enhance versatility in different cases. The absence of a fan eliminates noise but places more emphasis on system-wide airflow management. Users must carefully plan their builds, particularly in compact or airflow-restricted cases, to ensure optimal thermal performance. The NJ700’s packaging includes all essentials, such as cable ties and a comprehensive manual, providing a user-friendly setup experience.

Cooler Master X Silent Edge Platinum 850

Design and Build Quality

The Cooler Master X Silent Edge Platinum 850 is an innovative fanless PSU that supports up to 850W, a first in the industry for its kind. Built to the ATX 3.1 and PCIe 5.1 standards, it features advanced passive cooling via copper heat pipes and textured heat sinks, eliminating fan noise entirely. However, this design increases the unit’s weight and imposes installation constraints, requiring upright positioning and unobstructed ventilation. The package includes flexible, individually braided cables, with a right-angled 12V-2x6 cable for up to 600W GPU power delivery, emphasizing its suitability for modern high-performance systems.

Performance and Efficiency

The X Silent Edge Platinum 850 excels in load regulation, particularly on the 12V rail, maintaining tight voltage stability. However, testing revealed elevated ripple levels on the 5V and 3.3V rails, exceeding ATX specifications. Despite this, its excursion handling stood out, with impressive stability under transient loads, particularly for power-hungry GPUs. Efficiency was exceptional at high loads, achieving 94% at full load under 230V, surpassing even Titanium certification levels. It is also highly resilient to power interruptions, sustaining performance during brownouts up to 24 ms at full load.

Technical Specifications

As a fully modular ATX 3.1 PSU, the X Silent Edge Platinum 850 includes a 12V-2x6 cable supporting PCIe 5.1 GPUs. Rated for 0°C to 40°C operation, it provides all standard protections and features an OPP threshold engaging at 126% of its rated load. The build quality is supported by Cooler Master’s 15-year warranty, underlining the unit’s long-term reliability. However, ripple performance on secondary rails and a lower OPP threshold compared to competitors could present limitations for extreme use cases.

Installation and Usability

The passive design necessitates careful installation, with upright positioning and unobstructed airflow. Cooler Master explicitly advises against inverted or side mounting, which could compromise heat dissipation. The modular cable system simplifies assembly, and the included accessories enhance build flexibility. Integration with Cooler Master’s MasterCTRL software allows users to monitor key metrics, offering valuable insights for system optimization.

Cooler Master X Silent Edge 1100W

Design and Build Quality

Cooler Master’s X Silent Edge 1100W PSU is a significant milestone, delivering passive cooling at unprecedented wattage levels. The chassis integrates advanced heat pipe technology and substantial heatsinks, allowing the unit to dissipate heat efficiently without active cooling. Its robust build quality is complemented by meticulously soldered components, ensuring durability and thermal resilience. All design and production, including the PCB, cooling solution, and chassis, are handled in-house by Cooler Master. While the design choices are innovative, they rely heavily on analog controllers, limiting the full potential of the included digital MCUs.

Performance and Efficiency

The PSU demonstrates strong performance in load regulation, especially on the 12V rail, though the minor rails (3.3V and 5V) show room for improvement. Ripple suppression is effective but falls short of expectations in certain areas. Efficiency is a standout feature, surpassing 94% at high loads, but it declines at light and super-light loads. The platform excels in transient response on the 12V rail in standard tests, but performance drops during the demanding ATX 3.1 transient scenarios, particularly under extreme excursions. Its passive cooling handles thermal loads impressively, with no coil whine observed.

Technical Specifications

The X Silent Edge 1100W adheres to ATX 3.1 standards and features a modular interface with 16 sockets, including a native 12V-2×6 connection for PCIe 5.1 compliance. It uses a bridgeless PFC converter, LLC resonant topology, and synchronous rectification, with DC-DC converters for minor rails. Cooling is managed through a combination of four heat pipes and large heatsinks integrated into the chassis. The design includes redundant MCUs, currently underutilized due to firmware limitations. The inclusion of analog controllers adds unnecessary complexity and cost, which could be streamlined in future revisions.

Installation and Usability

The PSU’s modular design and individually sleeved cables simplify installation, while its length and connector spacing suit modern high-power systems. However, users must adhere to strict orientation guidelines to maintain airflow and thermal performance, limiting flexibility in some setups. Digital monitoring via Cooler Master’s MasterCTRL software provides valuable real-time data on temperature and load, enhancing usability for enthusiasts and professionals.

Conclusion

Fanless power supplies have evolved from experimental curiosities to serious high-performance components. Our review reveals that passive cooling technologies have reached a remarkable inflection point, with units like the Seasonic PRIME Fanless TX-600 and Cooler Master X Silent Edge proving that silent operation need not compromise performance.

The key breakthrough is efficiency—these 80 Plus Titanium certified PSUs consistently achieve over 94% efficiency, paired with innovative thermal management using heat pipes, extensive heatsinks, and strategically designed chassis. However, the technology demands careful system integration, with users needing to meticulously plan case airflow.

While premium pricing remains a barrier, these PSUs represent a significant engineering achievement, signaling a promising future for silent, high-efficiency power solutions in enthusiast and professional computing environments.