Power supply unit

A computer power supply unit converts AC mains electricity to stable DC voltages for internal components. Learn about technical specs and efficiency ratings.

About this subject

The power supply unit (PSU) is the component that converts alternating current (AC) from the wall outlet into direct current (DC) at the voltages required by computer parts, typically +3.3 V, +5 V, and +12 V. Without it, no hardware can operate.

Modern PSUs follow standards such as Intel's ATX12V and are rated by wattage, ranging from 300 W to over 1500 W for servers or mining rigs. A key metric is energy efficiency, certified by the 80 Plus rating (Bronze, Silver, Gold, Platinum, Titanium). An 80 Plus Gold PSU, for instance, guarantees at least 87% efficiency at 50% load, reducing heat waste and electricity costs.

Another important feature is modularity: non-modular (fixed cables), semi-modular, or fully modular. Modular units let you attach only the cables you need, improving cable management and airflow. Protections like OVP (over-voltage), UVP (under-voltage), SCP (short-circuit), and OPP (over-power) are critical to prevent damage to other components.

Choosing a quality PSU from reputable brands like Corsair, EVGA, Seasonic, or Cooler Master directly impacts system stability and longevity. Generic PSUs may deliver less power than advertised, use inferior components, and lack proper protections, posing risks of failure or even fire.

Frequently Asked Questions

What is the difference between modular and non-modular power supplies?

Non-modular units have all cables permanently attached, many unused. Modular units let you connect only the necessary cables, improving cable management and airflow.

What does 80 Plus Gold mean on a power supply?

80 Plus Gold is an efficiency certification. It means the PSU operates at ≥87% efficiency at 50% load, ≥90% at 100% load, and ≥85% at 20% load. Higher efficiency means less energy wasted as heat.

How do I choose the right wattage for my PC?

Add up the estimated power draw of all components (CPU, GPU, drives, etc.) and add a 20-30% safety margin. Use online calculators like OuterVision or Cooler Master, and select a reputable brand PSU matching the calculated wattage.