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How to Choose the Best PSU

Complete Beginner's Guide to Power Supply Specs and Features


Last Updated: February 12, 2025

Choosing the best PSU for your gaming PC build can be super confusing. To the untrained eye, looking at and comparing power supply specs is basically trying to decode alien language, and the clever marketing used by this and that company trying to convince you that their PSU is great doesn't make things easier. 

Then there's the conflicting advice you'll find online from fellow gamers and PC users, with some perhaps recommending you simply buy the cheapest PSU you can find to save money, and others who swear anything but buying the most expensive, absolute best power supply on the market will have your new system imploding within the week.

Like many things in life, the truth is somewhere in the middle, and what you should do (read: how much you spend on a PSU) depends entirely on your specific PC build. If you're building a high-end gaming PC with one of the best graphics cards on the market such as a NVIDIA GeForce RTX 4090, RTX 4080, RTX 4070 Ti, AMD Radeon RX 7900 XTX/XT, or RX 6900 XT, etc, sticking to the best PSUs on the market (or thereabouts) is wise. Providing systems that house powerful graphics cards and CPUs with enough clean, stable power from a quality, reliable, efficient power supply is important for the longevity and stable operation of your new beast.

For less powerful yet still capable gaming PCs, you don't necessarily need the best PSU out there, though you still want to remain above a certain level of quality to reliably power your system for many years to come. For the cheaper entry-level gaming PC builds on a tight budget, your PSU requirements aren't as stringent, but that doesn't mean you should rush out and buy that cheap no-name PSU. A golden rule of PC building you'll often hear within DIY circles is to never go too cheap on your PSU, and that saving a few bucks on that enticingly lower-priced yet potentially lower-quality unit may end up biting you later on.

Average or straight-up bad power supplies can cause all sorts of headaches down the road, such as buckling when under load (eg crashing your PC mid-game), providing less power in practice than what was listed on the spec sheet (eg a poor quality 650 watt PSU may turn out to fail at providing that amount of wattage), operating at less than desirable efficiency levels, running with loud noise all the time, or even worse such as prematurely dying on you which has the potential to damage all your other PC parts. In this guide we'll cover the important basics of choosing good PSUs including what the important specs actually mean in plain English, so that you can be a much savvier shopper for the rest of your DIY days.

Related: How to Install a PSU (& Which Way to Face)



What to Look for in a Good PSU

If you don't have time to read this whole FAQ (it's pretty long as I've tried to make this guide as comprehensive as I can), just read this section to get a quick overview of what to look for when choosing a good power supply for your new gaming system.

  • PSU Brand/Make. When buying PC parts or accessories, the brand of the product isn't always the most important factor. For example, when choosing a motherboard, there's only 4 main brands that all have good models, with no brand being clearly better or worse than the others overall in terms of their options. But with power supplies, the brand - or to be more specific, the make of the physical unit itself that may be sourced from another company - is a crucial consideration and the first thing to be aware of. NOT that PSU brand is the only factor, but it's important because different PSU brands source their units from different manufacturers, and the difference in quality can be substantial from one manufacturer to another. More specific information on good PSU brands is at the end of this guide.
  • Warranty Length. A quick tell as to the quality and reliability of a particular PSU is its included warranty period. In general, the longer the warranty included with a PSU, the more trust the manufacturer/brand has in that particular unit, and the better that model is going to be in terms of quality/reliability. The very best tier-A power supplies on the market will have a long 10 year warranty, sometimes even longer such as the 12 years of the Seasonic TX-1000. Most good mid-tier PSUs will offer at least 5 years warranty. If the warranty is 3 years or less, it's one sign you're potentially looking at a lower quality unit.
  • Professional Reviews. You can't solely judge a PSU by its spec sheet (though it does give clues), and while the brand is important as mentioned, it's not the be-all end-all factor (leading brands can sometimes release lower quality PSUs). Therefore, looking for the presence of favorable hands-on reviews on reputable hardware sites is key. If a certain model doesn't have any hands-on reviews, you may want to avoid it and go for a more known unit - there are many PSU options out there so there's no need risking an obscure no-name unit. Also keep in mind that while customer reviews are fine for getting additional viewpoints, they shouldn't be your only source of information as you need very specialized knowledge and equipment to properly assess the merits (or lack thereof) of a PSU. A ton of reviews along the lines of "It works! PC didn't blow up yet! 5 stars" doesn't change the fact that said PSU in question could be one to avoid at all costs - you just don't know.
  • Weight. Not likely to be relevant when choosing a PSU these days, as if you're like most people you'll probably buy your PC parts online, but it's worth mentioning. A quick tell to know how a PSU stacks up in terms of quality is its physical weight. Lower quality PSUs feel noticeably lighter compared to higher quality units. Generally speaking, the more "weighty" or "meaty" a PSU feels in your hands, the better quality its internals are.
  • Efficiency Rating. Not necessarily an indicator of quality, the efficiency rating of a PSU is still an important spec though, and any good PSU worth its weight (pun intended) will have an efficiency rating of at least 80 Plus Bronze or 80 Plus Gold. The efficiency rating is exactly as it sounds; how efficient the unit is in terms of power usage. I'll cover a bit more on efficiency ratings below if interested.


How Important is the PSU for a Gaming PC?

The PSU is an often-overlooked part of a gaming computer, but it makes sense that many newcomers to PCs and/or DIY assume that it isn't an important component to think about.

“It’s just a power supply. I’ll buy the cheapest I can find to save money”

Such thinking could come back to haunt you later, as you could say that a computer is only as strong as its weakest link. Building a decent gaming PC with a bad power supply is a recipe for disaster over the coming months or years, especially if you're using a high-end graphics card and doing a lot of gaming or other demanding workloads.

While a power supply won't directly affect gaming performance, and in many cases (pun intended) there's no need to buy a top of the line premium PSU, if you want a reliable PC over the long haul that won't fail prematurely and/or put your other expensive components at risk, there's a certain baseline of quality you should stick to when choosing a power supply. Besides failing on you, lower quality power supplies have other downsides such as typically lower efficiency levels leading to higher power bills, poor heat efficiency leading to higher noise and the potential to crash your system when under load, and some PSUs have bare cabling which can even leak RF energy (not good).



How Much Wattage Does a Gaming PSU Need?

Gaming computers vary greatly in power and performance, so the amount of PSU wattage you need can vary greatly too. Modern gaming desktops can require a PSU with a wattage of anywhere between 450 watts to 1000 watts. On average, for a typical mid-range gaming PC you'll likely need around 550 to 750 watts, with numbers less or more than that being for either super cheap budget PCs or extreme systems.

You don't want to simply guess your power supply wattage requirements though, so when planning a PC build you need to calculate roughly how much power your full list of parts will require (and don't forget accessories like hard drives and extra case fans). You then want to choose a PSU that has slightly more wattage than what you need.

So, if your parts list requires around 400 watts, then get a 500-550 watt unit to be safe, or even 600 watts if you'll potentially be doing solid upgrades to your build in future (such as upgrading the GPU, which can change your PSU requirements considerably). If you'll be overclocking your gaming computer, whether your CPU or GPU (either can be overclocked if you're wondering), you will also need to keep that in mind when choosing a PSU as overclocking will use more power.

Thankfully, there are online tools that make estimating the power consumption of your PC build easy. PCPartPicker's built-in wattage estimation is the most popular; simply select all the parts you're thinking of building, and it will show you an estimated wattage. From that number add on 100 or more watts depending on how much power headroom you want based on your usage and/or upgrade plans. There are other tools out there as well, such as the Outervision Power Supply Calculator, but PCPartPicker is the easiest and most user-friendly.



Power Supply Size Differences Explained

Another spec you may need to be aware of when choosing a power supply is its physical size, technically called the form factor. However, most power supplies on the market are of the same size - the ATX form factor (technically ATX12V) - which will fit in any ATX or microATX computer case (which covers the far majority of gaming computer cases on the market). For the most part, the only time you need to be concerned about the size of a power supply is when building in a very small mITX case, as some mITX cases require what's referred to as a SFX power supply. However, some mITX cases can fit an ATX PSU, so you don't necessarily need a SFX power supply for a mITX case. Always check the case specs.

Lastly, whilst unimportant for the majority of PC builds (so feel free to ignore this bit), sometimes the depth of a PSU is different. In other words, while the width, height, and screw placement is the same as other PSUs of the same form factor (eg ATX), the depth of that particular unit may be longer than usual. PSUs are typically 6 inches in depth, but certain powerful PSUs with high wattages may be deeper. If you want to be extra cautious that a certain large, beefy PSU will be compatible with a certain case (especially if said case is fairly compact in the length department), you may want to check if that case lists a spec related to PSU depth and check it against your PSU's depth. In the far majority of situations, you don't need to do this though, and any ATX PSU will fit in any ATX/mATX case.



What Are Modular PSUs & Are They Worth It?

Power supplies can be either modular, semi modular, or non-modular. A modular power supply (sometimes referred to as "fully modular") is one that has detachable power cables that allows you to remove certain connectors that you don't need to use for your PC. The benefit of this is having less cable clutter within your finished system, and specifically more freed-up space within the bottom of your case (where power supplies are installed in almost all modern PC cases) since you can detach any power cables that you won't need to use (such as extra SATA or PCIe power cables).

Modular power supplies can also make installation a little easier, especially in smaller cases, as well as making power supply cable management a bit simpler (less cables to manage). Furthermore, the extra room within the bottom of your case afforded by a modular PSU may also lead to slightly better airflow within your system (and perhaps less dust build-up). 

All of this sounds great, so why would you not buy a modular PSU? Price - modular PSUs cost a little more than semi-modular and non-modular PSUs, though not necessarily all that much (sometimes a modular model can only cost 10 to 20 dollars more than a same/similar non-modular unit). Whether or not you should spend the extra money on a modular PSU is down to personal preference and your particular PC build.

If you're on a budget, non-modular PSUs may be the way to go if you want to save as much money as possible, especially if working in a roomy mid-tower or larger. In general, the smaller the case the more convenient having a modular PSU will be. If budget isn't a big concern and you want the easiest, most flexible solution, stick to modular PSUs.

Semi-modular PSUs are also a great option, and not much different to modular (ie fully modular) PSUs. Semi-modular PSUs have a few cables that can be attached as needed (and detached if not needed), but also some permanently attached cables like the main motherboard and CPU connectors (which you would never need to detach anyway).


Modular vs Non-Modular PSUs. Modular = more expensive but less clutter


Does Power Supply Efficiency Rating Matter?

Power supplies have various efficiency levels which is one measure of how good a particular unit is. More efficient PSUs not only draw less power, meaning lower energy bills, but they produce less heat and therefore less noise as well. The efficiency of a power supply is given a rating, with "80 Plus" being the bare minimum rating you should go for. Meaning, if a unit doesn't have "80 Plus" mentioned somewhere then chances are you should avoid it.

There are always exceptions to the rule though, but in general opt for a 80 Plus unit or better whenever you can. There are levels to 80 Plus ratings, with basic 80 Plus, then 80 Plus Bronze, Silver, Gold, and Platinum, in order from least to most efficient. For super powerful gaming computers you'll want a gold rated PSU or better for maximum efficiency.


PSU efficiency ratings from least efficient (left) to most (right)


Which PSU Connectors Do You Need?

Not all PSUs have the same connections

Another thing you may need to consider when choosing a power supply are the power connectors, as different units come with different types and amounts of cables. For most gaming PC builds, if you buy a good-quality, popular PSU and your build is a pretty standard modern setup without much extra add-ons, chances are you don't have to worry about checking the PSU connections. But for more advanced and/or higher-end builds, or if you just want to be extra safe, it's something you'll want to double check.

First of all, all computer power supplies will have either a 24 or 20+4 pin main motherboard connector, and either a 4 or 8 pin 12V connector, both of which connect to the motherboard. But what you'll want to check is that your PSU has the right type and amount of power connectors for your graphics card - if your card requires dedicated power (most mid to high-end GPUs do). Some GPUs will require just 1 PCIe 6 or 8 pin cable, while others may need 2 of these. Most modern PSUs will come with 2 6+2 PCIe cables though (which can connect to either a 6 or 8 pin GPU connector), so you should be good, but if your GPU needs 2 of these PCIe connectors then be sure your PSU does indeed have 2 PCIe connectors.

For advanced users, if you’re running multiple cards in SLI or CrossFire you'll want to also confirm your PSU is either SLI or CrossFire compatible as not all are. It should specifically be listed in the PSU specs, but keep in mind some units won’t officially list support for SLI/CrossFire but are still capable of powering multi-GPU setups (in which case you'll need to dig a bit deeper to find out if your PSU is good to go for this).

If you have a ton of accessories for your PC build, check that your PSU has enough SATA or Molex 4pin connectors for your hard drives, optical drives, and other devices like case fans (which may actually require those older Molex connectors). Most modern PSUs will come with plenty, but you never know if you have a lot of components to hook up. Lastly, if you just arrived in a time machine from 10,000 years ago and you're including a floppy disk drive in your new build, check your PSU has such a connector as floppy drives require their own type of PSU cable.

See Also: How to Connect PSU Cables (& Cable Management)



What Are PSU Rails? (Single vs Dual Rail)

This is a more advanced topic, hence why I've left it to last, so don't feel like you need to understand PSU rails in order to choose a power supply for your build. It can be handy to know though, especially when deciding between different high-end power supplies for a powerful high-end rig. Power supplies are made up of different "rails" that transfer power from the PSU to your components, with the most important to know about being the 12V rail which is the one that provides power to your most powerful parts (including the CPU and GPU).

In a typical gaming computer the graphics card will require the most power, and so you’ll want to get a PSU that has at least 24A (amps) on the 12V rail if you have a single mid to high end GPU, and at least 34A for a high-end multi GPU NVidia SLI build. These are general guidelines, so if you want to be super prudent about your PSU choice it's best to find out exactly what your particular GPU will require.

There are basically two different types of PSUs out there (in regards to its rails). Single rail, and dual/multi-rail PSUs. Single rail units have a single high-powered 12V rail to power all your parts, while PSUs with multiple rails have more than one 12V rail each with different amperages to divide power between two or more rails.

Whether a unit has single or multiple rails doesn’t affect its overall performance, and if your build only requires a lower-power PSU such as 550 watts or less, the single vs dual rail PSU issue does not matter and either will be fine (so long as you still pick a decent quality PSU).

But for power users, a multi rail power supply will offer an extra layer of protection in case there's a short circuit, and when you start heading into enthusiast and real high-performance PC territory that use huge 1000 watt PSUs or higher, multi-rail PSUs start to become a whole lot more crucial as it's risky and dangerous to output so much power on only the single rail.



What Are the Best PSU Brands?

Choosing a good PSU isn't solely about selecting by brand and brand alone, as companies produce and/or sell different models that can vary in quality (sometimes quite significantly). However, there are certain PSU brands that consistently offer top-notch, reliable models, and have stood the test of time. The following are some of the best PSU brands you can mostly trust on the current US market, but still do your research on the specific model/s you're considering:

  • Seasonic (has mostly Tier A units)
  • SuperFlower (mostly Tier A units)
  • Corsair (has Tier A units, but also tier B/C units)
  • EVGA (has Tier A units, but also tier B/C units)
  • XFX (has Tier A units, but also tier B/C units)
  • Be Quiet (has Tier A units, but also tier B/C units)

Doesn't mean you shouldn't buy a PSU from a brand that's not on this list, as the above names simply represent the very best PSU brands overall based on their track record over the past few years (and based on my opinion). You'll find some decent PSUs from other companies like Gigabyte, Silverstone, Thermaltake, Asus, and Cooler Master just to name a few that come to mind, but you'll find plenty of PSU models to avoid from these brands (or that would only be suitable for mid tier or budget builds, but depends on the specific model in question and your build).

There are also plenty of other PSU brands out there that I haven't mentioned, but I didn't mention them for a reason as they're likely not worth considering (unless I missed a good one). Also, it's worth repeating as well that not ALL power supplies from the list above are great, as most of them produce a variety of units that range in quality. Choosing a good PSU is not just about brand but also about researching and comparing specific models as the same brand can vary in quality a fair bit.



Are Corsair RMX PSUs Good? (and RMX vs RME)

The RMX series are among the best power supplies out there today, and one of Corsair's best offerings. Corsair have a mix of great, good, and average PSUs, but the RMX is unquestionably a tier A unit no matter the metric used. Don't make the mistake of confusing the RMX series with the similarly named RM series (without the 'x'), as the latter is a slightly inferior unit (though still of good quality).

For strong graphics cards like the RTX 4080/5080 or RX 7900 XT or equivalent, combined with top CPUs like a modern Ryzen 7/9 or Intel Core i7/i9, you want to do everything you can to get a capable, reliable, quality PSU, and a Corsair RMX won't disappoint.

The downside is they don't come cheap, but it's a worthy investment in my opinion if building a powerful system. The RMX is also perfectly suitable for even a RTX 4090/5090, so long as you get a model with enough wattage (850-1000 watts or more, depending on all the parts in your build) as the RMX series comes in 550, 650, 750, 850 and 1000 watt models.

Also, there's the latest "e" models from Corsair, such as the RM750e, which are like a budget version of the standard RMX models yet are still of high enough quality to be recommended for powerful gaming PCs. So long as you find them cheaper than the standard RMx, they are a decent option to save money. The difference between the RMx and the RMe models is that the 'e' models have lower quality capacitors (Chinese, compared to the Japanese capacitors of the RMx) and a smaller fan which could lead to slightly higher noise.



Are SuperFlower PSUs Good?

Lesser known to the masses, SuperFlower are a very well respected PSU manufacturer who have made top quality units for other companies like EVGA in the past. EVGA and SuperFlower parted ways recently, and now the latter are selling their units direct to the US market. This recent entry into the direct-to-consumer business is the reason why SuperFlower isn't as well known in the PSU market compared to companies like Corsair, Seasonic, and EVGA (at least for now), but don't be fooled as they are some of the best quality PSUs on the market without a doubt.



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