The power supply is the component people think about last and should think about more. It’s the part quietly feeding every other component, and getting the wattage wrong means either wasting money on capacity you’ll never use or — worse — starving your build and causing crashes you’ll spend weeks misdiagnosing. The good news is that working out how many watts you need isn’t complicated. Here’s a straightforward 2026 guide to sizing your PSU without the guesswork.

Why wattage matters

Every component in your PC draws power, measured in watts. Your power supply has to deliver at least as much as everything combined pulls at peak, with margin to spare. Too little and the system becomes unstable — random restarts, shutdowns under load, or a PC that won’t boot at all when the GPU spikes. Too much and you’ve simply overpaid for headroom you’ll never touch. The goal is comfortably enough, not wildly excessive.

The two components that actually drive the number

Here’s the thing that simplifies the whole calculation: two parts account for the overwhelming majority of your power draw. Everything else is a rounding error by comparison.

  • The GPU. Your graphics card is usually the single biggest power draw in the system, and it’s the one that spikes hardest under gaming load. This is the number that matters most.
  • The CPU. Your processor is the second biggest, especially higher-end chips under heavy multi-core load.

Add those two together, add a modest allowance for everything else — motherboard, RAM, drives, fans — and you have your real draw. The rest of the parts sip power; a couple of SSDs and some fans barely move the needle.

A simple way to calculate it

You don’t need to add up every component by hand. The reliable method:

  1. Find your GPU’s recommended PSU wattage. Every graphics card lists a manufacturer-recommended power supply size on its spec page. This figure already builds in the rest of a typical system, which is why it’s such a useful shortcut.
  2. Sanity-check against your CPU. If you’re pairing a very high-end CPU with the card, nudge up a tier. A mainstream CPU needs no adjustment.
  3. Add headroom. Aim to run at roughly 60–80% of the PSU’s rating under full load. That keeps the unit in its efficient, quiet, long-life zone and leaves room for future upgrades.

Manufacturer GPU recommendations are deliberately a little conservative, which works in your favour — they leave the headroom baked in. Follow them and you’ll rarely go wrong.

Rough wattage tiers for 2026

To give you a ballpark before you check your specific parts:

  • Budget build (entry-level GPU, mainstream CPU): a quality 550–650W unit is plenty.
  • Mid-range gaming build (mid-tier GPU, solid CPU): 650–750W is the comfortable sweet spot for most people.
  • High-end build (upper-tier GPU, high-end CPU): 850W gives you room to breathe.
  • Flagship build (top-end GPU that spikes hard, high-core CPU): 1000W or more, and check the GPU’s specific guidance, as the most powerful cards have short, sharp power spikes that reward extra margin.

Notice how narrow that range is. Most real gaming builds land at 650–850W. If you’ve calculated a need for 1200W and you’re not running a flagship card, re-check your numbers — you’ve probably overshot.

Watts aren’t everything: efficiency and quality

A power supply’s wattage tells you how much it can deliver, not how good it is. Two more things matter, and skimping here is a false economy since the PSU touches every other part.

Efficiency rating (80 Plus). This tells you how much wall power is actually delivered versus lost as heat. 80 Plus Bronze is a fine baseline; Gold is the popular value sweet spot, running cooler and quieter. Higher tiers exist but the returns diminish for most builds.

Build quality. A cheap, no-name PSU is the one component that can fail dramatically and take other parts with it. Stick to reputable brands and well-reviewed units. This is genuinely not the place to save your last few dollars — a good power supply protects everything plugged into it, and often outlives two or three builds. Don’t buy used ones, either.

Connector types: check before you buy

Wattage is only useful if the PSU has the right cables. Modern high-end GPUs may use the newer 12V-2×6 power connector (you’ll also see it called 12VHPWR), while others use one or more traditional 8-pin PCIe connectors. Before buying, confirm your PSU provides the connector your specific graphics card needs, or that a suitable adapter is included in the GPU box. It’s a small detail that stalls builds when overlooked, and it’s covered alongside other gotchas in our guide on choosing compatible parts.

Modular or not?

A quick practical note. Fully modular power supplies let you attach only the cables you need, which makes cable management and airflow much easier. Semi-modular is a fine middle ground. Non-modular units have every cable permanently attached, which means stuffing unused cables somewhere out of the way. It doesn’t affect performance, but modular makes for a tidier, better-breathing build.

The bottom line

  1. Start from your GPU’s recommended PSU wattage — it does most of the work for you.
  2. Bump up a tier if you’re running a very high-end CPU alongside it.
  3. Aim to sit at 60–80% load: 650–850W covers most gaming builds.
  4. Buy a reputable unit, 80 Plus Gold is the value sweet spot, and never buy used.
  5. Confirm it has the right connectors for your graphics card before you order.

Sizing a power supply feels intimidating because it sounds electrical and precise, but in practice it comes down to your graphics card plus a bit of margin. Get a quality unit with sensible headroom and the right cables, and you’ll never think about it again — which, for the component silently keeping your whole PC alive, is exactly how it should be.

Related guide: How to Diagnose a PC That Won’t Boot