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Article: How much PSU wattage do I need?
How much PSU wattage do I need?
To size a power supply, add your CPU's rated power and your graphics card's rated board power, add an allowance for the rest of the system, then pick a PSU that puts your typical gaming load near the middle of its rating. Also check the GPU maker's recommended PSU wattage, and choose whichever number is higher.
The power supply is easy to overlook when you're focused on the CPU and GPU, but it feeds every part in your build. Here's how to size one, what 80 PLUS ratings mean, and why ATX 3.1 and the 12V-2x6 connector matter for modern graphics cards.
How do I calculate how much wattage I need?
Add the rated power of your two biggest components, add an allowance for everything else, then add headroom. The CPU and GPU account for most of a gaming PC's power draw, so their official ratings are the numbers that matter.
- CPU: use the processor's rated power from Intel or AMD. Use the higher turbo or boost power limit if one is listed.
- GPU: use the card's total board power (TBP or TGP) from the GPU or card maker.
- Everything else: add an allowance for the motherboard, memory, storage, fans, pump and lighting. These parts draw far less than the CPU and GPU combined.
- Headroom: choose a PSU rated well above that total, so normal gaming sits around the middle of the PSU's range and short power spikes don't push it to its limit.
- Cross-check: compare your result with the GPU maker's recommended PSU wattage, and use the higher figure.
What does a worked example look like?
Here's the method with example numbers. Swap in the ratings for your own parts.
| Component | Example rating |
|---|---|
| CPU rated power | 125 W |
| GPU total board power | 300 W |
| Rest of system allowance | 75 W |
| Estimated load | 500 W |
| PSU that puts this load near 60% of its rating | 850 W |
An 850 W unit runs this example at about 59% of its rating, with room for power spikes and future upgrades. A 650 W unit would technically cover 500 W, but at about 77% load with less margin.
Why does PSU headroom matter?
Headroom keeps the PSU in its efficient range, keeps its fan quieter, and gives you margin for power spikes and upgrades. 80 PLUS efficiency requirements peak at 50% load, which is why sizing for a mid-range load makes sense.
- Efficiency: PSUs are typically most efficient near half load (see the table below).
- Noise: less load means less heat, so the fan spins slower. Some PSUs stop the fan entirely at low loads.
- Upgrades: a bigger GPU later won't automatically require a new PSU.
What do 80 PLUS Bronze, Gold and Platinum mean?
80 PLUS is a certification for PSU efficiency, meaning how much of the power drawn from the wall reaches your components instead of becoming heat. Each tier sets a minimum efficiency at specific loads. Higher tiers waste less power.
Efficiency is easy to picture. A PSU that's 90% efficient and delivering 450 W to your components draws about 500 W from the wall. The other 50 W becomes heat inside the PSU. Less waste means less heat, a quieter fan and a slightly lower power bill.
| 80 PLUS tier (115 V internal) | 10% load | 20% load | 50% load | 100% load |
|---|---|---|---|---|
| 80 PLUS (Standard) | — | 80% | 80% | 80% |
| Bronze | — | 82% | 85% | 82% |
| Silver | — | 85% | 88% | 85% |
| Gold | — | 87% | 90% | 87% |
| Platinum | — | 90% | 92% | 89% |
| Titanium | 90% | 92% | 94% | 90% |
| Ruby | 91% | 93% | 95% | 91% |
Source: CLEAResult 80 PLUS, PSU ratings explained. Ruby also requires 85% efficiency at 5% load. Requirements for 230 V EU units are higher at each tier.
Gold is a common choice for gaming builds: meaningfully more efficient than Bronze without the cost of the top tiers. Some PSUs also carry a Cybenetics rating, an independent certification that tests efficiency and noise across many load points.
What are ATX 3.1 and the 12V-2x6 connector?
ATX 3.1 is Intel's current revision of the desktop PSU design guide. It specifies the 12V-2x6 connector, a 16-pin cable that can deliver up to 600 W to a single graphics card. ATX 3.x PSUs are also designed to handle the brief power spikes modern GPUs produce.
- 12V-2x6: an updated version of the earlier 12VHPWR 16-pin connector. Its sense pins tell the GPU how much power the cable can supply.
- Native cable: if your GPU has a 16-pin power connector, a PSU with a native 12V-2x6 cable avoids adapters.
- Install it right: push the connector in until it's fully seated, and avoid a sharp bend right at the plug.
Source: Intel ATX Version 3 Multi Rail Desktop Platform Power Supply Design Guide.
What else should I look for in a power supply?
Beyond wattage and efficiency, check the form factor, cable setup and protections. These affect how easy the PSU is to install and how well it protects your components.
- Form factor: ATX for most cases. SFX for many small form factor cases.
- Modularity: a fully modular PSU lets you attach only the cables you use, which keeps the build tidy.
- Protections: look for over-voltage, under-voltage, short-circuit, over-temperature, over-power and over-current protection (OVP, UVP, SCP, OTP, OPP, OCP).
- Connectors: make sure there are enough PCIe and CPU power connectors for your GPU and motherboard.
Don't cut corners on the PSU. A low-quality unit can fail in ways that damage other parts, so a reputable, certified PSU with full protections is worth prioritizing.
Which NZXT power supplies fit common builds?
- C850 Gold Core is an 850 W, ATX 3.1, 80 PLUS Gold and Cybenetics Platinum PSU. It's fully modular, has a 600 W 12V-2x6 cable, and is rated 92.1% efficient at 50% load (115 V). View product
- C1000 Gold Core provides 1000 W with the same ATX 3.1 spec, 80 PLUS Gold rating, fully modular design, 12V-2x6 cable and Zero RPM Fan Mode. View product
- C850 SFX Gold brings 850 W, ATX 3.1 and 80 PLUS Gold to an SFX unit measuring 125 x 63.5 x 100 mm, for small form factor builds. View product
Compare every model in power supplies.
Quick checklist
- Look up your CPU's rated power and your GPU's total board power.
- Add an allowance for the rest of the system, then add headroom.
- Cross-check with the GPU maker's recommended PSU wattage.
- Choose an efficiency tier (Gold is a common choice for gaming).
- For a 16-pin GPU, choose an ATX 3.1 PSU with a native 12V-2x6 cable.
- Match the form factor (ATX or SFX) and confirm the case's PSU length limit.
- Confirm full protections and enough connectors.
FAQ
Is 750 W enough for gaming?
It depends on your CPU and GPU. Add their rated power, add an allowance for the rest of the system, and compare the total with the GPU maker's recommendation. If 750 W leaves your typical load near the middle of its range, it's enough.
Can a PSU be too powerful?
A higher-wattage PSU only supplies the power your parts ask for, so it won't harm them. The downsides are cost and lower efficiency at very light loads, so pick enough headroom, not the biggest number available.
Is 80 PLUS Gold worth it over Bronze?
For PCs that game for long sessions, Gold's higher efficiency means less heat and a quieter PSU, with modest power savings over time. Bronze can be a sensible choice for lighter use on a tighter budget.
Do I need an ATX 3.1 power supply?
If your graphics card uses a 16-pin power connector, an ATX 3.1 PSU with a native 12V-2x6 cable is the cleanest option. For GPUs with 8-pin connectors, any quality PSU with enough wattage and connectors works.
Does PSU efficiency affect performance?
No. Efficiency doesn't change frame rates. It changes how much power is lost as heat, which affects noise, temperatures inside the PSU and your electricity use.
