How to Pick a Power Supply

Your system’s power supply plays a vital role by making sure that all the components in your build receive clean and stable power to do their respective jobs.

If you’re doing your first build or upgrading your current system, it’s a good idea to plan for an adequate power supply to suit your needs.

To get a rough idea for the total wattage you’d want to look for, you’ll need to establish a baseline for your system. You can get a good idea for this by adding the power draw of your chosen CPU and graphics card since they’ll usually be the components that draw the most power (compared to other components like your DRAM or SSD).

1. Search online for the TDP or power draw for your specific graphics card. Different manufacturers will likely tweak things which may cause similar cards from other manufacturers to draw more power.
2. Now repeat this for the processor you plan to pair your graphics card with.
3. Add 150W to fill in as a rough estimate for your system components (motherboard, fans, memory, storage, peripherals)
4. Then add another 150W to your total to serve as further headroom. This will help ensure that the components you’ve picked so far will operate within the power supply's efficiency curve as well as account for future upgrades to your system.

If you're lucky enough to own an RTX 4080 or 4090, then we've actually done the work for you, so take a look at our best PSU for RTX 4080 and best PSU for RTX 4090 pages for handy shortcut.

Most power supplies will vary between 80% and 96% efficiency depending on the quality of the components the power supply is built with and how heavy a load is placed on the power supply itself.

Efficiency in this sense is how well the power supply will turn AC power from a wall outlet into usable power for your components (the leftover 4-20% is wasted as heat).

So, an efficient power supply will convert as much AC power into usable DC power for your components and produce as little heat as possible while doing it.

Size

Most builds will use an ATX power supply, this is more or less a standard for the cutout on the case that the power supply will mount to. That said, the depth of a power supply can differ between different wattages (higher-rated power supplies will generally take up more space). Thankfully, most case manufacturers will list the maximum PSU dimensions their cases will accommodate.

Small form-factor builds can be found that use an ATX power supply, but the smaller, SFX and SFX-L standard is becoming more commonplace amongst SFF case manufacturers. The difference between SFX and SFX-L is the total depth, with SFX-L being the larger power supply (and higher wattage).

Modular vs. Non-Modular

Once you’ve picked the form-factor for your power supply, it’s time to decide between modular and non-modular (or semi-modular).

A modular power supply will have no cables permanently attached. Allowing you to plug in just the cables you need to power your components and even swap out for custom cables in different colors and lengths, making them a great option that can help you keep cable management nice and tidy.

A semi-modular power supply offers a similar benefit to a fully-modular power supply, but with the primary motherboard and CPU power cables permanently attached.

A non-modular power supply will have all cables permanently attached to the power supply itself, which may result in a challenge in cable management depending on the case you’re building with.

Fans

The fan in your power supply will work to keep its internal components cool, but they can also contribute to the overall noise produced by your system.

While most power supplies will operate with a fan curve that’ll ramp up the fan as needed, some feature a “Zero RPM mode” which will allow the fan to remain off during basic operation such as web browsing, then spin up once a more substantial load is placed on the power supply (such as gaming).

Control

One final thing to consider when picking a power supply, that isn’t absolutely crucial to its operation, is whether or not it offers some form of monitoring and/or control.

The vast majority of power supplies will simply rely on their own firmware to regulate temperature and other things within the PSU itself with no option for external control or monitoring.

High-end models such as the HXi and AXi series of power supplies will offer detailed monitoring of power flowing in and out of the PSU as well as control of the internal fan via an internal USB 2.0 cable connected to your motherboard.

And certain models will offer lighting control through an external button or port that can be connected to your lighting controller.

We hope that this has helped you sort through your power supply options. To help streamline the process of picking a power supply, we’ve got a PSU Calculator that helps you dial down your choices based on your preferred CPU and graphics card. And if you’re planning on a full build, check out our PC Builder which’ll help you map out your build from start to finish! If you're more of a visual learner, the video below from our boy Nick should help.