HOW OW MANY WATTS DO YOU NEED?
It’s usually not as many as you think. A decent single graphics card gaming rig is happy with 500–600W. Put very roughly, a nicely specced modern rig with multiple drives needs 200–250W at most, plus the CPU and graphics card.
We did consider offering a quick list of what uses what—a 10TB hard drive, for example, needs 7–10W—but the list would be too long, and there are online calculators that can do this for you. OuterVision has a good one that includes processor and GPU overclocking, plus it shows potential savings obtained by using higher efficiency ratings.
Plan ahead. Are you ever going to fit two graphics cards, or overclock? Specify for the most extreme your rig is ever going to get—you do not want to buy twice. Given the graphics system is where the pressure is, look for recommendations from graphics card manufacturers. For example, an Nvidia GTX 1080 Ti or GTX Titan asks for 600W, and 850W if you double up. Drop to a GTX 1060, and 450W will cover things.
AMD cards are more demanding—the Vega 64 is notoriously power-hungry. A single Vega 64 wants 600W, but a dual rig asks for 1,100W. The most extreme recommendations include a dual Vega 64 Liquid Edition or quad GTX Titan; these want 1,350W. A four-card Radeon R9 Fury X tops this at 1,600W. Yowsers.
If you plan to overclock, another 50– 100W should cover things, but you need a good clean current, so go high quality. There is no ideal value. It just needs to be enough to run everything without stressing the PSU—an extra 100W over won’t hurt; much more means paying for something you’ll never use.