How to Choose a PSU: Wattage, 80 Plus and Cable Types

The power supply is the one part that can take the rest of the build with it. Size it correctly, understand what 80 Plus really means, and read a teardown review.

Every other component fails alone. A power supply can fail loudly, taking the graphics card and the drives with it, and a marginal unit causes crashes that look like driver problems. It is also the component with the most misleading marketing, so a little knowledge goes a long way.

Sizing the wattage

1. Add up the real power draw: processor package power, graphics card board power, then roughly 50 to 100 watts for drives, fans, memory and the board.
2. Add headroom for transient spikes. Modern graphics cards can briefly pull double their rated board power, and that instant is what trips an undersized unit.
3. Aim for 20 to 30 percent above your peak estimate, which also lands you in the efficiency sweet spot where the unit runs quietly.
4. As a rough guide: integrated graphics 400-450 W, mid-range card 650-750 W, high-end card 850-1000 W, a high-end processor with a flagship card 1000-1200 W.

What 80 Plus actually means

The 80 Plus badge rates efficiency at converting wall power to DC, not quality. A Gold unit wastes less electricity and produces less heat than Bronze at the same load, but a bad Gold can still be worse than a good Bronze in ripple, transient response and protection circuits. Treat certification as a floor, then look for a teardown review that measures ripple, hold-up time, over-current protection and fan noise. Warranty length is a decent proxy: seven to ten years signals the maker expects it to last.

Cable types and connectors

• Fixed cables are cheapest and always present, with spare bundles cluttering the case.
• Semi-modular keeps the essential cables attached and lets you add the rest. Good value.
• Fully modular is easiest to build with and to route cleanly, at a small price premium.
• Check the number of separate PCIe cables, not just the connectors. High-draw cards want one cable per connector, not a daisy chain.
• For new high-power graphics cards, use the vendor's own cable for the 12V-2x6 connector, seat it fully, and avoid sharp bends near the plug.
• Prefer an ATX 3.x unit if you are building new. The standard was written for exactly the transient spikes that trip older designs.

Common buying mistakes

• Assuming more watts means better. A 1200 W unit under a 200 W load is less efficient and no safer.
• Buying a no-name high-wattage unit because the number is impressive and the price is not.
• Ignoring the connector count, then discovering you are one cable short on build day.
• Reusing a decade-old power supply from a prebuilt in a new build with a modern graphics card.

Pick a well-reviewed unit from a reputable platform with the right wattage and cables, and you will never think about it again. That is exactly what you want from a power supply.