Mini ITX or SFX PC Power Supplies? Compared by Specs
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Choosing between a Mini ITX and SFX PC power supply depends on your case constraints and power needs. Both units offer 80 Plus Gold efficiency, ensuring reliable performance with less wasted energy. The primary difference lies in their physical dimensions and output capacity. You must match the form factor to your chassis mounting points. This comparison breaks down the key specifications to help you decide which unit fits your build.
Key differences
| Aspect | FSP 400W Gold Flex ATX Mini ITX Power Supply | SilverStone 700W SFX 80 Plus Gold Power Supply |
|---|---|---|
| Form Factor | Mini ITX | SFX |
| Wattage | 400W | 700W |
| Modularity | not listed | Fully Modular |
| Fan Size | 4 cm | 92mm |
| Dimensions | 1.6 x 3.25 x 5.9 inches | 3.94 x 2.5 x 4.92 inches |
Which one should you choose?
Choose FSP 400W Gold Flex ATX Mini ITX Power Supply if
- You need a compact 400W unit for low-power systems like NAS or industrial applications.
- Your case requires a Mini ITX form factor with a 4 cm fan.
- You prioritize a smaller footprint with a width of only 1.6 inches.
Choose SilverStone 700W SFX 80 Plus Gold Power Supply if
- You require higher power output up to 700W for gaming or workstations.
- You want fully modular cables for cleaner cable management.
- Your case supports the standard SFX mounting holes and a 92mm fan.
Verdict: The FSP unit suits small, low-power builds where space is extremely tight. The SilverStone unit is better for higher-performance systems needing more wattage and flexible cabling. Choose based on your case's form factor support and your system's power requirements.
ITX vs SFX PSU Specs
Form Factor
Product A is a Mini ITX unit, measuring 1.6 inches in width, 3.25 inches in height, and 5.9 inches in length. Product B follows the standard SFX form factor, with dimensions of 3.94 inches wide, 2.5 inches high, and 4.92 inches long. The SFX unit is slightly shorter but significantly wider. You must check your case compatibility, as the SFX model is not compatible with ATX mounting holes. The Mini ITX design offers a more compact footprint in width, which may suit smaller chassis better.
Wattage
Power output is a critical differentiator between these two units. Product A provides 400W of continuous power. Product B delivers 700W, offering a substantial increase in available energy for your components. If you plan to install a high-end graphics card or multiple drives, the 700W unit provides much more headroom. The 400W unit is suitable for basic systems or low-power builds. Your choice depends entirely on the total power draw of your PC components and whether you need extra capacity for future upgrades.
Modularity
Cable management affects airflow and case interior cleanliness. Product B is a fully modular power supply, meaning you can connect only the cables you need. This reduces clutter and improves air circulation inside your case. The data for Product A does not specify its modularity, so you cannot assume it is fully modular. If Product A is non-modular, you will have unused cables taking up space. For tight Mini ITX builds, the fully modular design of Product B is a significant practical advantage.
Efficiency Rating
Both units share the same 80 Plus Gold efficiency rating. This certification ensures that both power supplies convert AC power to DC power with high efficiency, reducing waste heat and electricity costs. Product A specifies an efficiency greater than 90%. Product B also meets the Gold standard for high efficiency. Since the efficiency tier is identical, neither unit holds an advantage in this specific category. You will benefit from similar energy savings and thermal performance regardless of which unit you choose.
Voltage Regulation
Stable power delivery protects your components from damage. Product B features a class-leading single +12V rail with strict 3% voltage regulation and low ripple. This ensures your CPU and GPU receive steady power under load. The data for Product A mentions low ripple and noise but does not provide specific voltage regulation percentages. Without explicit data for Product A, you cannot confirm if it matches the strict 3% standard of Product B. The explicit specification for Product B makes it the safer choice for sensitive electronics.
Choose the right PSU for your build
Users with tight Mini ITX case constraints
Your case likely requires a Flex ATX form factor. This unit measures 1.6 inches wide and 3.25 inches high, fitting into tight spaces where standard SFX units will not fit. The 400W output is sufficient for low-power systems, and the 4 cm fan ensures it fits within the strict depth limits of small form factor builds.
Users needing high power and cable management
This SFX unit delivers 700W of power, which is significantly higher than the 400W option. It is fully modular, meaning you only connect the cables you need, reducing clutter. The 92mm fan runs quietly at 18 dBA, and the Japanese capacitors provide stable voltage regulation, making it ideal for more demanding hardware setups.
Users prioritizing silent operation and efficiency
Both units are 80 Plus Gold, but this SFX model features a large 92mm fan. Larger fans move more air at lower speeds, resulting in quieter operation compared to the smaller 4 cm fan in the Mini ITX unit. The fully modular design also helps with airflow inside your case, keeping components cool and quiet.
Quick picks
| # | Product | Best for | Price |
|---|---|---|---|
| 1 | FSP 400W Gold Flex ATX Mini ITX Power Supply | Compact builds needing efficient power | Check price of FSP 400W Gold Flex ATX Mini ITX Power Supply on Amazon |
| 2 | SilverStone 700W SFX 80 Plus Gold Power Supply | compact Mini ITX builds needing high efficiency | Check price of SilverStone 700W SFX 80 Plus Gold Power Supply on Amazon |
The products compared
FSP 400W Gold Flex ATX Mini ITX Power Supply
Best for: Compact builds needing efficient power
- Form Factor
- Mini ITX (what this guide is about)
- Wattage
- 400W
- Efficiency Rating
- 80 Plus Gold
- PCIe Connector Type
- 6+2 pin
- Fan Size
- 4 cm
- Dimensions
- 5.9 × 1.6 × 3.25 inches
View on Amazon: FSP 400W Gold Flex ATX Mini ITX Power Supply Affiliate link
This FSP unit is a 400W Mini ITX power supply with 80 Plus Gold efficiency. It uses a small 4 cm fan for quiet operation. The design fits tight cases and includes a PCIe 6+2 pin for graphics cards. It suits users building compact systems that need reliable power without taking up much space.
Pros
- 80 Plus Gold efficiency rating over 90%
- Compact 4 cm fan for low noise
- Includes PCIe 6+2 pin connector
- Resettable power shutdown protection
Cons
- Lower 400W output compared to 700W alternatives
- Smaller 4 cm fan may run louder under load
- No mention of full modularity in specs
Good fit if
- You need a compact power supply for a Mini ITX case
- You require 80 Plus Gold efficiency for better power savings
- You are building a system with moderate power needs
Skip if
- You need more than 400W of power
- You prefer a larger 120 mm fan for quieter operation
- You require a fully modular cable setup
Verdict: FSP 400W Gold Mini ITX PSU delivers solid efficiency in a small form factor. It fits users who prioritize compact size and efficiency over high wattage or full modularity.
SilverStone 700W SFX 80 Plus Gold Power Supply
Best for: compact Mini ITX builds needing high efficiency
- Form Factor
- SFX (what this guide is about)
- Wattage
- 700W
- Efficiency Rating
- 80 PLUS Gold
- Modularity
- Fully Modular
- Fan Size
- 92mm
- Dimensions
- 4.92 × 3.94 × 2.5 inches
View on Amazon: SilverStone 700W SFX 80 Plus Gold Power Supply Affiliate link
The SilverStone SST-SX700-G is a 700W SFX power supply designed for compact Mini ITX builds. It features 80 PLUS Gold efficiency and fully modular flat cables. The unit uses a 92mm fan for quiet operation at 18 dBA. It delivers a strong single +12V rail with strict voltage regulation. This PSU fits small cases but requires SFX mounting holes, not standard ATX ones.
Pros
- 700W output on a single +12V rail
- 80 PLUS Gold efficiency rating
- Fully modular flat cables
- Quiet 92mm FDB fan at 18 dBA
Cons
- Heavier at 3.09 pounds than many competitors
- Requires SFX mounting holes, not ATX
- Smaller 92mm fan may spin faster under load
Good fit if
- You need high efficiency in a small form factor
- You want fully modular flat cables for tight spaces
- Your case supports SFX mounting holes
Skip if
- You require standard ATX mounting compatibility
- You need more than 700W of power
- You prefer a larger fan for silent operation
Verdict: SilverStone 700W SFX Gold PSU offers strong power density and efficiency for Mini ITX builds. It suits users who need modular cabling and quiet operation in a compact SFX chassis.
Specifications side by side
| Spec | FSP 400W Gold Flex ATX Mini ITX Power Supply | SilverStone 700W SFX 80 Plus Gold Power Supply |
|---|---|---|
| Wattage | 400W | 700W |
| Efficiency Rating | 80 Plus Gold | 80 PLUS Gold |
| Modularity | not stated | Fully Modular |
| PCIe Connector Type | 6+2 pin | not stated |
| Fan Size | 4 cm | 92mm |
| Form Factor | Mini ITX | SFX |
| Dimensions | 5.9 × 1.6 × 3.25 inches | 4.92 × 3.94 × 2.5 inches |
| Weight | 2 pounds | 3.09 pounds |
| Size | 400W_Gold | 700W |
| Model | FSP400-60FGGBA | SST-SX700-G |
| Color | not stated | Black?Lead-Free Paint? |
Frequently asked questions
Can a Mini ITX power supply fit in an SFX case?
No, they are not interchangeable. The Mini ITX unit measures 1.6 inches wide and 3.25 inches high. An SFX unit is 3.94 inches wide and 2.5 inches high. The physical dimensions differ significantly. You must match the PSU form factor to your case mounting holes. Using the wrong size will prevent installation.
Which power supply offers higher wattage for gaming?
The SFX unit provides 700W of power. The Mini ITX option is rated for 400W. If your build requires more than 400W, the SFX model is the only viable choice. Higher wattage supports more powerful graphics cards and processors in larger builds.
Do both units have 80 Plus Gold efficiency ratings?
Yes, both the Mini ITX and SFX options carry an 80 Plus Gold certification. This rating means they convert AC power to DC power with high efficiency. You will waste less energy as heat. This efficiency helps keep your system cooler and reduces power costs over time.
Is the SFX power supply fully modular?
Yes, the SFX unit is fully modular. You can connect only the cables you need. This reduces clutter inside your case. The Mini ITX unit does not list modularity in its specifications. You may need to manage unused cables if you choose the smaller form factor.
How much space does the Mini ITX PSU take up?
The Mini ITX unit measures 1.6 inches wide, 3.25 inches high, and 5.9 inches long. It weighs 2 pounds. This compact size allows it to fit in tight spaces where standard SFX units will not fit. It is ideal for very small form factor builds.
What is the weight difference between the two units?
The SFX unit weighs 3.09 pounds. The Mini ITX unit weighs 2 pounds. The SFX model is heavier due to its larger internal components and higher power output. The difference is small, but the Mini ITX unit is lighter overall.