How to choose a power supply (PSU): wattage, efficiency ratings and 12V-2x6 explained

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The power supply is the part most first-time builders spend the least time on, and the one that can take every other component with it when it fails. You do not need the most expensive unit on the shelf, but you do need to know what the numbers on the box mean and which of them matter.

Work out the wattage you need

Add up what your parts draw under load. In practice two components dominate: the graphics card and the processor. Everything else (motherboard, memory, drives, fans) adds comparatively little.

Start with the GPU maker's recommendation. Graphics card makers publish a recommended PSU wattage for each card, and it already allows for a typical system around it. It is the safest single number to go by.
Leave headroom. Modern graphics cards can draw short spikes of power far above their rated figure for a few milliseconds. A unit running near its limit all the time is louder, hotter and more likely to shut down under those spikes. Aim for your expected load to sit somewhere around half to two thirds of the PSU's rating.
Do not overshoot wildly either. A huge unit for a modest system costs more and gains you nothing. Buying a little extra for a future GPU upgrade is sensible; buying double is not.

Online PSU calculators are fine for a rough figure, but treat their results as a starting point rather than an answer.

Efficiency ratings: what 80 Plus actually tells you

The 80 Plus badge (Bronze, Silver, Gold, Platinum, Titanium) measures efficiency: how much of the power drawn from the wall reaches your components rather than being lost as heat. A higher tier means slightly lower electricity use, less heat and often a quieter fan. What it does not measure is overall quality. A Gold badge says nothing about the protections, the ripple on the output, or how well the unit copes with those spikes. Cybenetics runs a separate certification that also rates noise, and some reviewers prefer it, but the same rule applies: efficiency is one line on the spec sheet, not a verdict. For most gaming builds, a well-reviewed Gold unit is the sensible middle ground.

Modular, semi-modular or non-modular

Non-modular: every cable is permanently attached. Cheapest, but unused cables have to be stuffed somewhere in the case.
Semi-modular: the motherboard and CPU cables are fixed, the rest detach. A good compromise for most builds.
Fully modular: every cable detaches. Easiest for tidy cable management and small cases.

One firm rule: never mix modular cables between different power supplies, even from the same brand. The pin layout at the PSU end is not standardised, and the wrong cable can destroy a drive or a graphics card on first power-on.

Connectors for current graphics cards

Many graphics cards still use the familiar 8-pin PCIe power connectors. Higher-power cards use a single 16-pin connector instead.

That connector was first called 12VHPWR. The ATX 3.1 standard replaced it with a revised version named 12V-2x6, which keeps the same 600 W maximum but changes the pin lengths so that a plug that is not fully seated is less likely to deliver power.
A PSU described as ATX 3.0 or 3.1 has been designed with GPU power spikes in mind and usually comes with a native cable for the 16-pin connector, so you do not need an adapter.
Whatever the connector, push it all the way in until it clicks and there is no visible gap, and avoid bending the cable sharply right at the plug.
For cards with several 8-pin sockets, follow the card maker's guidance on using separate cables rather than one cable with two plugs on it.

Also check the basics: enough SATA power connectors for your drives, and the right CPU power connectors (some motherboards want two).

Quality over brand hype

Brands do not build every unit themselves. The same brand often sells excellent models and mediocre ones, made by different manufacturers. So judge the specific model, not the logo:

Read independent technical reviews that load-test the unit, not just unboxing videos.
Look for the standard protections: over-current, over-voltage, over-temperature and short-circuit protection.
A long warranty is a good sign that the maker trusts the unit.
Be wary of no-name units with suspiciously high wattage for the price, and of community "tier lists" that are years out of date.

A quick checklist

Note the GPU maker's recommended wattage and add sensible headroom.
Pick a well-reviewed unit, ideally Gold or better.
Check it has the connectors your GPU and motherboard need.
Choose the cable style that suits your case.
Keep the original cables with the original unit.

Planning a build and unsure whether your PSU is enough? Post your parts list in the comments and let others take a look.