A PSU (Power Supply Unit) converts alternating current from the wall into the regulated DC voltages, mainly 12 V, 5 V and 3.3 V, that computer components use.
Why it matters
An undersized or poor-quality PSU causes random shutdowns, crashes and can damage hardware. Capacity is measured in watts, and efficiency is shown by 80 Plus ratings such as Bronze, Gold and Titanium, which indicate how little power is wasted as heat.
High-end graphics cards can draw hundreds of watts in short spikes.
Quality units also provide protections such as over-current and over-temperature shutdown, which guard the rest of your parts.
Example
CPU: 125 W
GPU: 220 W
Other: 60 W
Total estimate: 405 W
Choose roughly 650 W for headroomPSUs run most efficiently around half load and have room for spikes.
Common mistakes
- Buying the cheapest unit for an expensive system.
- Choosing a PSU with too few connectors for the graphics card.
- Using old cables from a different modular PSU, which can have different pinouts.
Related
Get notified when this term updates
Plus occasional practical tips on uptime and monitoring, nothing else. Unsubscribe anytime.
This page is general information written by our editorial team and updated when documentation changes. Servers and providers differ, so test changes safely first. See our editorial policy and disclaimer.