Power Supplies: How to Choose One and Why Cheap Ones Are a Bad Idea

The power supply is the one component whose failure can take others with it, and it’s the one people economise on because it doesn’t appear in any benchmark. A bad PSU doesn’t make your machine slower. It makes it unstable in ways that look like every other fault, which is why they’re so often misdiagnosed.

Sizing it

Add up the realistic peak draw of the CPU and GPU, then add roughly 100W for everything else. Then add headroom, not because you’ll use it, but because efficiency peaks around half load and components draw brief spikes well above their rated figures.

Transient spikes are the reason for headroom. Modern graphics cards can draw double their rated power for a few milliseconds, and a PSU sized exactly to the average will trip its protection and shut the machine down under load. Which presents as random restarts during games and gets blamed on everything else first.

What the ratings actually mean

80 PLUS certification measures efficiency. How much wall power reaches the components rather than becoming heat. Bronze, Gold, Platinum and Titanium are progressively better.

Efficiency saves a little electricity and produces less heat and fan noise. What it doesn’t directly measure is build quality, ripple suppression or protection circuitry, and those are what determine whether a failure is graceful or takes your motherboard with it.

In practice the correlation is decent: manufacturers who bother with Gold or better usually bother with the rest. But a Gold-rated unit from an unknown brand is not safer than a Bronze one from a reputable one.

The protections that matter

• OVP / UVP. Over and under voltage protection.
• OCP. Over current protection, per rail.
• OPP. Over power protection.
• SCP. Short circuit protection.
• OTP. Over temperature protection.

Reputable units list these. Very cheap units often list some and implement fewer. This is the difference between a PSU that shuts down cleanly when something goes wrong and one that passes the problem downstream.

Connectors and cables

That fourth point is worth repeating because the connectors physically fit: modular cables are not interchangeable across brands, and using the wrong one can put 12V where the board expects ground.

When to replace one

• Random restarts under load, particularly in games, with temperatures fine.
• The machine won’t power on at all, or powers on and immediately off.
• Coil whine that’s got noticeably worse, or any burning smell.
• It’s a decade old. Capacitors age whether the unit is used or not.
• You’re upgrading the GPU and the new card needs connectors you don’t have.

Don’t carry an old PSU into a new build to save money. It’s the component most likely to fail, and the one whose failure is most expensive.

Glossary

Frequently asked questions

How many watts do I need?

Add your CPU and GPU peak draws, add about 100W for everything else, then choose a unit where that total is roughly 50-70% of its rating. That leaves headroom for transient spikes and sits near peak efficiency.

Is 80 PLUS Gold worth paying for over Bronze?

Usually, though less for the electricity saving than because manufacturers who certify Gold tend to build better units. Brand reputation is a better signal than the badge alone.

Can I use my old PSU in a new build?

If it’s high quality, under about five years old and has the right connectors, yes. If it’s a decade old or came free with a case, no. It’s the wrong place to save money.

Why does my PC restart during games but not otherwise?

A classic sign of a PSU that can’t handle transient spikes, particularly one sized exactly to average draw. Temperatures being normal makes it more likely rather than less.

Do I need to worry about the 12VHPWR melting reports?

Mostly it came down to partially-seated connectors. Push it fully home until it clicks, don’t bend the cable sharply right at the plug, and check it after moving the machine.

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