Where Is the PSU in Your Computer? A Quick Hardware Guide

The Power Supply Unit (PSU) is the metal box that converts wall AC power into clean DC voltages for every component. Here’s where to find it and what to know.

Standard ATX Tower (Most Desktops)

• Location: Top-rear or bottom-rear of the case.
• Identify: Metal box with AC inlet (IEC C14), power switch, voltage selector (115/230V), and cable bundle exiting into the case.
• Mounting: 4 screws from outside rear panel. Fan faces down (bottom mount, draws cool air from under case) or up (top mount, exhausts into case — older design).

Form Factors

• ATX (PS/2): 150×86×140 mm — standard.
• SFX / SFX-L: Small form factor (125×63.5×100 / 130 mm) — mini-ITX cases.
• TFX: Thin (85×65×175 mm) — slim prebuilts (Dell, HP SFF).
• Flex ATX: 150×86×100 mm — proprietary OEM.

Key Connections (What Plugs In)

• 24-pin ATX: Motherboard main power.
• 8-pin (4+4) EPS: CPU power.
• 6/8-pin PCIe: GPU power (1–4 connectors).
• SATA / Molex: Drives, fans, RGB, accessories.

Buying/Replacing Tips

• Wattage: GPU + CPU max draw × 1.5 = target (e.g., RTX 4080 + i7-13700K → 850–1000W).
• Efficiency: 80 Plus Gold (standard), Platinum/Titanium (premium).
• Modular: Fully modular = only plug cables you need (cleaner build).
• Size clearance: Check case max PSU length (cables add ~30mm).

Safety

Unplug & hold power button 10s before opening. Capacitors hold lethal charge. If unsure, have a pro swap it.

The PSU is the heart — hidden, heavy, and absolutely critical. Don’t cheap out.