Any · Hardware

Size your PSU before the next upgrade

A power supply that's too small is the quiet cause of random shutdowns under load. Sizing it right takes one calculator and ten minutes.

DifficultyMedium
Time15 min
RiskLow
ReversibleYes
PlatformAny
UpdatedAug 18, 2026

Written and tested by emdottech

What that means

Low risk. This fix only checks things, or changes settings you can switch back in the same place. This change is reversible — you can return to the previous state without professional help or data loss.

PSU sizing in four moves — adding up CPU and GPU draw at 80%, buying about 30% headroom over that total, choosing 80 Plus Bronze or better, and using native GPU cables with no daisy-chains

Steps

01
- Add up your parts' typical draw (CPU + GPU are 80% of it) — be honest about the GPU you're planning, not the one you have
02
- Buy ~30% headroom over that total: a 450 W system wants a 600–650 W unit, which also runs cooler and quieter at part load
03
- Pick 80 Plus Bronze or better — it's a minimum efficiency floor, not a quality award, but it filters out the worst
04
- Prefer native cables (the PSU maker's own) over adapters for your GPU; one good cable beats two daisy-chained ones

How to verify the fix

Your calculated draw plus about 30% headroom matches the PSU you choose, and native cables (no daisy-chained adapters) are available for your GPU.

If this didn't fix it

Random shutdowns under load continue after the upgrade — the PSU was still undersized or a cable is faulty; re-check the calculation.

Next stop: the related fixes below, or start a guided diagnosis.

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Size your PSU before the next upgrade

Steps

✓How to verify the fix

!If this didn't fix it

Related fixes

How to verify the fix

If this didn't fix it