PSU (Power Supply Unit)
Converts AC wall power to the DC voltages your PC components need. Rated by wattage and efficiency (80 Plus certification). Critical for system stability.
What does a PSU do?
The PSU converts AC power from your wall outlet (120V or 240V) into the DC voltages your PC components need: 12V for the CPU and GPU, 5V and 3.3V for drives and peripherals. It's the foundation of system stability — a bad PSU can cause crashes, damage components, or even pose a fire risk.
Wattage sizing: Add your CPU TDP + GPU TDP + ~100W for other components, then add 20-30% headroom. A system with a Ryzen 7 9800X3D (120W) and RTX 5070 (250W) draws ~470W, so a 650-750W PSU is appropriate.
80 Plus efficiency ratings
80 Plus certification indicates power conversion efficiency: 80 Plus (80%), Bronze (82%), Silver (85%), Gold (87%), Platinum (89%), Titanium (92%). Higher efficiency means less heat, lower electricity bills, and generally better component quality. 80 Plus Gold is the sweet spot — good efficiency without the premium price of Platinum/Titanium.
Frequently Asked Questions
How much wattage do I need?
For a mid-range gaming PC (Ryzen 5 + RTX 5070): 650W. For high-end (Ryzen 7 + RTX 5080): 850W. For enthusiast (Ryzen 9 + RTX 5090): 1000W+. Always buy more wattage than you need — PSUs run most efficiently at 50-80% load.
What is ATX 3.0?
ATX 3.0 is the latest PSU standard that includes the 12VHPWR (or 12V-2x6) connector for modern GPUs and supports higher transient power spikes. If buying a new PSU in 2026, get ATX 3.0 to avoid needing adapter cables for your GPU.