what power supply do you need for a local AI PC? A simple wattage guide

Building a local-AI rig and unsure how big a PSU to buy? Here's the simple wattage math for single and dual GPUs — plus why power-limiting lets you… Aliteq Ravi Malhotra · Hardware Editor

RTX 4090 build: ~850W minimum, 1000W for headroom (card is 450W).

PSU wattage at a glance

RTX 5090 build: 1000W on ATX 3.1 with the 12V-2×6 connector (575W, spikes 700W).

PSU wattage at a glance

Dual GPU (2× 3090 or 4090): 1500-2000W.

PSU wattage at a glance

Add ~150-200W for CPU, RAM, drives, and fans on top of the GPU(s).

PSU wattage at a glance

Local-AI trick: power-limiting cards for inference lets a smaller PSU do more.

PSU wattage at a glance

Buy quality — 80+ Gold or better, ATX 3.1 for any 50-series card.

PSU wattage at a glance

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