How to Choose PC Parts: The Power Supply

TSTonyV

If you’re reading this post, you’re probably here for one reason: you want to build a new PC. Whether it’s your first time building or you’re an experienced builder and just need some extra clarification, this post is for you. With all the options available on the market, it can be overwhelming, but we’re here to help break it down.

 

If you’re looking for other parts as well, be sure to check out some of our other guides:

How to Choose PC Parts: The Processor

How to Choose PC Parts: The Motherboard

How to Choose PC Parts: The Video Card

How to Choose PC Parts: RAM

How to Choose PC Parts: SSDs and Hard Drives

How to Choose PC Parts: The Case

This guide will go over how to choose a power supply unit. The power supply unit (PSU) is another major internal component to select for a PC build and generally one of the last pieces to choose. We only have one important question this time:

• What other parts do you have in your system? Every one of your PC components draws power. Some more than others. The biggest power draw is going to be your graphics card, followed by the processor. High-powered graphics cards and processors draw more power than lower-end ones. If you have multiple GPUs, you have to power both. You need to pick a power supply unit that can adequately match the power demand on your system. 

Things to know when picking a power supply:

What does 80+ certified mean? (80+ bronze, 80+ gold, etc.)

If you’ve ever looked up computer power supplies, you’ve probably seen them labeled “80+ Bronze,” or something similar. This is the efficiency rating system for power supply units. 

80+ Plus certification is a standard that certifies computer power supplies having at least 80% energy efficiency at 20%, 50%, and 100% load. In other words, it wastes 20% or less of the electricity it’s drawing from the electrical circuit. There are different levels of 80+ Rating, with different levels of efficiency, as shown in this image:

This image was sourced from https://www.clearesult.com/80plus/program-details/. You can find more information about the 80+ certification standard at that link.

These numbers are calculated based on the power output divided by the power draw. For example, an 80+ rated 500W power supply at 100% load (full power) would output 500W of power to your computer, but draw 625W from the wall because it's only 80% efficient. If it was at 50% load (half power), it would output 250W of power and it would be drawing ~313W from the circuit because it's 80% efficient at 50% load.

In comparison, an 80+ Gold rated 500W PSU at 100% load would be outputting 500W of power, but only drawing ~575W from the wall because it's 87% efficient. That same PSU at 50% load would output 250W, and draw ~278W from the wall because it's 90% efficient at 50% load. 

What is a modular power supply?

Modular power supplies allow you to attach and detach power cables as needed, keeping cords limited to the pin connector you'll actually need. This is mostly useful for cable management because you can use only the cables you need and don’t have to worry about any that are just hanging free. Semi-modular power supplies are an in-between with some cables that cannot be detached and others that can. 

Modular power supply:

 

Semi-modular power supply: 

Power Supply Form Factor

Like motherboards, power supplies have a form factor, which designates the size/mounting specifications. ATX power supplies are the most common. You may also see SFX, ITX, and TFX, which have a small form factor.

The important thing here is that you need to make sure the case you choose for your build supports the form factor of the power supply you’re using. The majority of cases will support ATX. Some small form factor cases will only support SFX and/or ITX. 

How big of a power supply do I need?

We covered this a bit in our graphics card guide as well. Before selecting a power supply, pick your graphics card. All graphics cards have a “recommended power supply.” Most PC builders should base their decision on that recommendation, as it’s considering your total system power consumption. So if you have a graphics card that recommends a 650W power supply, you can safely stick with that. You may be able to go a little bit under depending on your exact setup, but try not to go too far or your system won’t work properly.

Picking a power supply above the recommended specifications for your card isn’t a problem either. If you’re planning on doing future upgrades on your system, getting a high-quality power supply now with enough headroom to run high-end parts can be a great choice and save money in the long run. A 650W power supply isn’t going to overpower and fry a video card that only recommends 500W. You can safely run it, and if you buy a higher-powered card in the future, you won’t have to worry about getting a new power supply to go with it.

One quick note, the recommended power supply assumes you’re running a single GPU in your system. If you’re running multiple, you’ll need to figure out how much power your GPUs are drawing individually and factor that in. A 650W power supply isn’t enough to run a system with two RTX 3080s that can each draw over 300W and a high-end processor drawing potentially 200W. For a configuration like that, you’d need something like an 850W, possibly higher depending on exactly what parts you’re running. 

What power supply should you buy?

If there is one thing in your system that you absolutely should not cheap out on, it’s the power supply. The power supply is the heart of your system. Every component is powered and driven by it. That $20 500W power supply you saw might be tempting when you’re on a budget, but a bad power supply could ruin every single part of your computer. 

When it comes to picking a power supply, we always recommend one that’s at minimum 80+ certified. I’d personally go with 80+ Bronze or higher. You don’t have to buy the craziest, most expensive 1500W 80+ Titanium power supply if you’re making an entry-level gaming PC, but don’t go for the cheapest power supply either. 

80+ Bronze and 80+ Silver are good for entry-level and mid-range builds (though 80+ silver power supply units are uncommon). For higher-end builds, stick with 80+ Gold or better. And remember, just because it’s an entry-level build, doesn’t mean you can’t get yourself a nice 80+ Gold power supply. While the higher-rated power supplies are more expensive, they tend to have higher quality internals. Entry-level performance still likes high-quality power delivery, and a good power supply will last you a very long time. High-end power supplies usually have very long warranties, upwards of seven or even ten years for the really good ones. 

It’s best to evaluate power supplies individually. Many brands will produce very high-quality lines of power supplies while also having some that are poor quality. Check reviews online and do some research to make sure what you’re getting is reliable. There are several lines of PSUs from different manufacturers that are generally known for being high quality, such as the Seasonic FOCUS, EVGA Supernova, and Corsair RM/RMx series of PSUs. You should always double-check and do some research, though! 

Here are a few recommendations for power supplies we carry at different 80+ certifications. There are more available than just these, but this should be a good starting point.

80+ Bronze: Good for budget, entry/low-mid level systems

Powerspec 650 Watt 80+ Bronze ATX Semi-Modular PSU

Corsair CX550M 550 Watt 80+ Bronze ATX Semi-Modular PSU

EVGA 650BQ 650 Watt 80+ Bronze ATX Semi-Modular PSU

80+ Gold: Good for all systems, including high-end. 

Seasonic FOCUS GX-650 650 Watt 80+ Gold ATX Fully Modular PSU (Also comes in 750W and 850W variants)

Corsair RM750 750 Watt 80+ Gold ATX Fully Modular PSU (Also comes in 650W and 850W variants)

EVGA Supernova 850 G+ 850 Watt 80+ Gold ATX Fully Modular PSU

Cooler Master V650 650 Watt 80+ Gold SFX Fully Modular PSU

80+ Platinum/Titanium: These will work for any system but should generally only be bought with very high-end systems/multi-GPU-based systems due to the price and wattages these come in. 

ASUS Rog Thor 1200 Watt 80+ Platinum ATX Fully Modular PSU

EVGA Supernova 1200P2 1200 Watt 80+ Platinum ATX Fully Modular PSU

Seasonic USA Prime TX-850 80+ Titanium ATX Fully Modular PSU

Corsair AX1600i 1600 Watt 80+ Titanium ATX Fully Modular PSU

Once again, I can’t say this enough, remember that your PSU is the heart of your system! If there’s one thing in your computer that you should never compromise on, it’s the power supply. 

 

If you have follow-up questions, feel free to comment below, and if you’re still looking for part recommendations, we have guides for Processors, Motherboards, Graphics Cards, RAM, Hard Drives, and Cases.