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How to Choose a PC Power Supply

What to consider when buying a power supply for your computer.

PC Power Supply

Last Updated: September 6, 2022

Written by Kevin Jones

When building a computer, many people overlook the importance of choosing a good power supply. Usually this is because it's not very exciting or doesn't provide obvious benefits to the finished product.

However, a good power supply does more than just provide electricity to your system. It can deliver clean and stable voltage to avoid system crashes. A power supply unit needs to provide enough juice for the computer to run. Choosing the right power supply for your computer can save you a lot of headaches in the future. Using the wrong power supply can not only shorten the lifespan of your components but can also damage them. Suppose a power supply can't handle the power load of all the components in your build. In that case, you may experience crashes, freezes, data loss, or component failure.

A high-quality power supply unit (PSU) is essential for creating a reliable computer that will last.

If you’re building a new PC or replacing an existing power supply and aren't sure how to pick a good power supply to match your needs, then this guide is for you.

Check out my Recommended PSUs below.

Best 750–1000 Watt PSU

What to Look for in a Power Supply

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The main job of a power supply is to convert the alternating current (AC) from your wall outlet into the direct current (DC) needed by the components inside your computer.

Power Efficiency

PSUs with higher efficiency ratings use less energy and produce less heat, improving their reliability and reducing noise.

The 80 PLUS certification program for power supplies helps to promote energy efficiency by indicating its efficiency rating.

Higher efficiency power supplies may have a higher upfront cost. However, they could potentially save you money on electricity in the long run.

Lower wattage PSUs will be more power-efficient even when idle. For this reason, you may be able to save more on electricity by getting the correct wattage of PSU than by getting the one with the best 80 PLUS rating.

PSU Efficiency Levels (115 V)
Certification Level10% Load20% Load50% Load100% Load
80 Plus 80% 80% 80%
80 Plus Bronze 82% 85% 82%
80 Plus Silver 85% 88% 85%
80 Plus Gold 87% 90% 87%
80 Plus Platinum 90% 92% 89%
80 Plus Titanium 90% 92% 94% 90%

Power Output

An important factor when buying a PSU is the supported wattage.

You can estimate your power needs by using the following chart.

Component Peak Power Usage
Top-Tier CPU (e.g. Intel's i9-12900K) 241 W
Mid-Tier CPU (e.g. Intel's i5-12500) 117 W
Top-Tier Graphics Card (e.g., Nvidia RTX 3090) 350 W
Mid-Tier Graphics Card (e.g., Nvidia RTX 3060) 170 W
Motherboard 80 W
Optical Drive 30 W
3.5" Hard Drive 9 W
M.2 or 2.5" SSD 9 W
140 mm Case/CPU Fan 6 W
120 mm Case/CPU Fan 6 W
80 mm Case/CPU Fan 3 W

By adding up these numbers, you can estimate peak power usage.

Check estimates for a specific CPU:

With four SSDs and three large case fans, a top-tier computer could see peak usage of 737 W.

It's generally a good idea to add a 100–150 W buffer to your expected usage. This buffer will give you some flexibility in case of miscalculations and will allow you to add more drives, fans, or add-in cards in the future.

In the above top-tier computer example, a 900 W power supply would be a reasonable choice.

In most cases, buying a little more wattage than you need is a safer choice for ensuring system stability.

Don't forget to account for the additional power required for overclocking if you intend to overclock your CPU or GPU. Overclocking could require roughly an extra 50–100 W, depending on how much you overclock these devices.

Cables

Connectors

Make sure your PSU has the correct connectors to support the hardware in your system. Cheaper PSUs may cut costs on connectors and cables by offering fewer options and shorter lengths.

Check with your motherboard and graphics card documentation to determine which connector types are needed. Buy a popular, recently-released PSU; it will likely have the necessary connectors for a new PC build. However, if you use old components or an old power supply, you may find some incompatibilities.

Here are some common connector types that power supplies support:

  • 24-pin connector for the motherboard
  • 4/8-pin connector for the CPU
  • 6/8-pin connectors for graphics cards
  • SATA Power connector for each SATA HDD or SDD storage device

The latest graphics cards and PSUs are starting to support a new 16-pin PCIe 5.0 connector that replaces multiple 8-pin connectors.

Modular Cables

Typical power supplies come with various cables to connect your components. However, extra unused power cables can work against you by interrupting airflow.

In comparison, modular and semi-modular power supplies allow for attaching only the cables you need. As the name implies, semi-modular power supplies have some wires soldered on, while you can optionally connect others.

Cable Lengths

Most power supplies will have cables long enough to support mid-sized towers comfortably. If you have a full-size tower, you may want to check reviews and documentation to ensure that the cables are long enough to allow good cable management.

Power Supply Form Factors

Various form factors are available for power supplies, but most PC gamers will want the standard ATX power supply.

Small form factor PSUs allow for usage in many computer case shapes, including mini-PCs.

Power Supply Features

Overvoltage protection and short circuit protection can help to save your components in the case of a surge or accident.

LED lighting is another feature you might consider, depending on the goals for your PC build.

Choosing a Cost-Effective Power Supply

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Perhaps you don't personally pay the power bill or don't expect the computer to have heavy daily usage. In those cases, the lower upfront cost of a less efficient PSU may be the better choice.

On the other hand, if you care more about the electric bill or the environment and plan to maintain a higher CPU usage, then a more efficient PSU may be better.

Don't go too far over 150 W above your expected power needs. Rightsizing your power supply will keep electricity costs to a minimum, as higher wattage PSUs will consume some additional power, even when idle.

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  • Titanium 80 PLUS efficiency rating means the Seasonic Prime TX is at least 94% efficient at 50% load.
  • Fully modular cabling allows you to optimize airflow and minimize clutter.
  • Silent during low usage.
  • 12-year warranty.
  • This series of power supplies comes in power outputs including 750, 850, and 1000 watts.
  • It also is available in a Gold rated (GX) version. Seasonic Prime TX-750 Seasonic Prime TX-750 Check Price on Amazon Amazon Affiliate Link

Other Considerations When Building a PC

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Want to brush up on other new technologies to consider when building a computer? Check out these articles: