When you’re preparing to build a new PC, the first topics on your mind are likely powerful multi-core processors, fancy high-end graphics cards, ultra-fast NVMe storage, or maybe even unique case lighting and effects. But one component that often fails to get the attention it deserves is the power supply. After all, virtually every other component in your PC can be affected by the type, quality, and capabilities of your PSU.

That makes the process of choosing the right power supply just as important as any other component. Therefore, here’s a quick high-level overview of the factors you should consider when looking at power supplies for your next PC build.

Power Supply Wattage Link to heading

The first step in choosing a power supply is determining your required wattage. Choosing the correct wattage is important: going too low will prevent your components from performing at their expected level, cause system instability, and can even damage components. Going too high wastes money that could be spent elsewhere, although it won’t hurt the components.

Despite the marketing hype around 1000W+ units, most systems—even high-end ones—don’t need more than 650–750W. Tools like PSU calculators can help estimate the correct wattage based on your planned build.

Some calculators (e.g., from be quiet!) also check for connector compatibility, warning you if your GPU or CPU power needs exceed a PSU’s available outputs—even if the wattage is sufficient.

Power Supply Form Factor Link to heading

ATX Link to heading

ATX is the most common power supply form factor. Modern ATX PSUs comply with the EPS standard, supporting dual 4-pin or single 8-pin CPU connectors. Dimensions:

  • Width: 150mm
  • Height: 86mm
  • Depth: 140–200mm+ depending on wattage and design

Make sure your case supports the depth of the chosen PSU.

SFX / SFX-L Link to heading

SFX (Small Form Factor) PSUs are ideal for compact builds. Standard dimensions:

  • Width: 125mm
  • Height: 63.5mm
  • Depth: 100mm

SFX-L extends depth to 130mm to allow larger fans and higher wattages. They’re more expensive at the same wattage but are necessary for small cases. You can use adapters to mount SFX PSUs in ATX cases.

Power Supply Efficiency Link to heading

The 80 PLUS program certifies power supplies by efficiency. Tiers include:

  • 80 PLUS (basic)
  • Bronze
  • Silver
  • Gold
  • Platinum
  • Titanium (highest)

More efficient PSUs generate less heat and waste less power. Look for at least 80 PLUS Bronze for general use, and Gold or better for high-end or always-on systems.

Summary Link to heading

Selecting the right PSU ensures system stability, safety, and long-term performance. Focus on:

  • Wattage: Match your component needs
  • Form factor: Ensure it fits your case
  • Efficiency: Higher is better for performance and power savings

A good PSU is an investment in your entire build—don’t treat it as an afterthought.