How To Tell Power Supply Wattage May 2026

You learn that wattage isn’t just a number. It’s a promise. And not all promises are kept. A $20 700W PSU is a fire in a box. A $100 450W unit from a trusted brand can run a system that draws 440W, because it’s built to deliver its rated power continuously, not just for the first five minutes. The sticker tells you peak wattage or sustained? Most don’t say. You have to know.

Four hundred and fifty watts.

So you learn to read the label like a crime scene. The +12V rail—that’s the one that matters. CPUs and GPUs drink from it like marathon runners at a water station. If the label says “+12V @ 30A,” that’s 360W. Not 450W. The rest of the wattage is split across +5V and +3.3V, which your hard drives and USB ports sip politely. A 450W PSU with weak +12V is a 360W PSU pretending to be brave. how to tell power supply wattage

You contort your phone beneath the PSU and snap a photo. Blurry, but readable. A sticker with logos, certifications, warnings in six languages, and then—smaller than the barcode, smaller than the serial number—the number you need: . You learn that wattage isn’t just a number