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How to Choose a Power Supply

Size it with headroom, check the connectors your graphics card needs, and do not save money on this part.

Beginner 2 min readBy the VantaSpec teamUpdated

Why it matters

The power supply feeds every other part. A good one runs quietly for years; a poor one can shut the PC down under load, and in the worst case damage what it is connected to. It is the last part to economise on.

How many watts

  1. 1Find the graphics card maker's recommended power supply wattage. For most gaming PCs this is the number that matters most.
  2. 2If you are adding up parts yourself, use the processor's and graphics card's maximum power figures and add around 100 W for everything else.
  3. 3Leave headroom on top: a supply running well below its limit is quieter and copes with brief power spikes from modern graphics cards.

Tip: The PC builder adds up the power your chosen parts draw and warns if the supply is too small.

What 80 Plus ratings mean

80 Plus ratings (White, Bronze, Silver, Gold, Platinum, Titanium) say how little power is wasted as heat. A Gold unit wastes less than a Bronze one, so it runs cooler and often quieter, and costs a little less to run.

Careful: An efficiency rating is not a quality rating. It says nothing about the protections, the parts inside or how long the unit lasts. A newer standard, Cybenetics, also measures noise; where a unit has both, both are worth reading.

Connectors

  • 24-pin for the motherboard, and one or two 8-pin CPU power plugs. High-end boards often want two, so check the board's manual.
  • PCIe power for the graphics card: either 8-pin plugs or, on many newer cards, a 12V-2x6 cable. Units built to the ATX 3.0 or 3.1 standard usually include the newer cable.
  • SATA power for drives and many fan and lighting hubs.

Modular or not

A fully modular supply lets you plug in only the cables you use, which makes a tidier build and better airflow. Semi-modular units have the motherboard and CPU cables fixed and the rest detachable. Non-modular units are cheapest but leave spare cables to hide.

Careful: Never mix modular cables between power supplies, even of the same brand. The pins at the supply end are not standard, and the wrong cable can destroy parts.

Size and warranty

Most cases take a standard ATX power supply; small cases may need SFX. The case's specifications say which. A long warranty is a good sign that the maker expects the unit to last: good units are often covered for seven years or more.

Compare the same model across UK shops on its product page before buying. Choosing parts that work together covers the other checks for a full build.

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