Not to worry. You can figure out a good PSU match on your own.All you have to do is settle on the key specs needed for yourbuild, then go hunting for specific models that fulfill thosecriteria. We've listed and explained them below, in the order ofmost important to least important for gaming builds. Some of theserelate to practical concerns, like having enough power, but otherstake into account aesthetics as well.> Not building a gaming PC? You may find our general advice on buying a power supply morehelpful.
A power supply's number one job is to provide enough power for aPC's components, no matter what type of computer you're building.But calculating that number takes a bit more math than looking upthe TDP (thermal design power) spec for each component, adding upthose wattage numbers, and then buying a PSU close to thetotal.
You need more wattage than that. A surplus, commonly calledheadroom, allows your power supply to run at peak efficiency. Italso gives you the ability to add parts or upgrade to componentswith higher power requirements (or both), depending on the amountof headroom you go for.This 750W power supplyis ideal for an upper mid-range or lower high-end gaming PC.
Alaina Yee / IDG
So how much headroom should you target? That depends on yourcurrent budget and your future upgrade plans. Your baseline will bea range of 40 to 80 percent of the wattage rating—you should stickwithin those boundaries for peak efficiency. Pick the lower end ofthat if you intend to overhaul your rig with a much beefier CPU-GPUcombo down the road and don't want to buy a new power supply toaccommodate those changes. (This strategy works best if you plan todo those updates within the PSU's warranty period.) Choose thehigher end if you don't plan to do power-hungry upgrades or reusethe PSU in a new build with more powerful hardware.
An old-school rule of thumb is to aim for 50 to 60 percent useof the wattage rating. You'll have plenty of room for upgrades, andyou won't have to worry about the effect of ambient temperatures onactual amount of power available. Many modern builders don't likesuch a large buffer, though, citing improved power efficiency inPSUs (see below). Neither attitude is inherentlywrong. It doesn't hurt to be closer to 40 percent usage than 80percent—you won't draw more power at the wall with a higher wattagePSU. That's based on what your components actually pull, not thewattage rating. But you can end up overspending on something youdon't make full use of.Outervision's detailedpower supply calculator can help you calculate your wattage needs.
If you use Outervision's popular online calculator to do allthis math for you, you'll encounter the modern attitude. For moreheadroom, simply go for a power supply with a higher wattage. Wesuggest padding the headroom when working with cheaper powersupplies or living in an area with hot weather.
Here's how this shakes out in a concrete example: After doingthe math yourself (or consulting an online calculator), you findout your system's total draw is 300W. If you're on a budget withmodest hardware, you could buy a cheaper 500W power supply, likethe EVGA 500 W1. Got a little more cash? You canalso go up to a 750W power supply, like the Cooler Master Masterwatt 750, and ensure thatyou'll have the power needed for a later jump up to a high-endgraphics card. (You know, when they're widely available again.)
Alaina Yee / IDG
Usually the lower the wattage of a power supply, the fewer powercables it has. Go low enough and this point is a bit moot—generally, systems requiring a 400W or lower PSU just don't haveenough components to need a ton of power cables. Cost alsoinfluences the number of cables. Pricier models generally offermore.
You have to be most attentive to this point when attempting tocram a bunch of parts into a PC while also not spending a lot on apower supply. Go too low and you just won't have enough cables foreverything you plan to put in your system. Sure, maybe your wattagerequirements are met, but imagine this scenario: Your graphics cardand sound card both require additional power, but sit at a widedistance from each other on the motherboard. If you only have onePCIe cable, you're going to be in a bind. (Plus, it's not idealrunning those on the same cable anyway.) This example is for alower-end build, but you can encounter this issue in higher-endprojects, too.
Avoid this problem by going over your list of parts and tallyinghow many cables of each type you'll need. Factor in any futureupgrades you're anticipating, too—for example, going from agraphics card with a single 6- or 8-pin connector to one with twopower connectors. You can run a graphics card on one cable, but ifyou live in a warm climate, it may be optimal to use two separatecables for each connector to reduce the risk of the cablesoverheating.
You can see the difference for yourself by comparing severalPSUs. For example, the Cooler Master MWE Bronze 500 offers just fivecables: one each for ATX 24-pin (motherboard), EPS 8-pin (CPU),Molex (fans/accessories), SATA (storage/optical drives), and PCIe6+2 (GPU/expansion cards). Go up in wattage to the Cooler Master MWE White 550, and you get anadditional SATA and PCIe cable. But increasing wattage doesn'tguarantee more cables—the dirt-cheap EVGA 500 N1 has just one PCIe cable (and apiddly two-year warranty).
Power supply efficiency tells you how much actual power you canexpect to get from a power supply. While the wattage tells you thetheoretical amount provided, the power efficiency rating indicateshow much power you should expect to have after losing some to heatand other causes.
These days most everything is 80 Plus-rated or higher. Atminimum, these power supplies provide 80 percent of its advertisedwattage at 20-, 50-, and 100-percent load. (That's the metric bywhich the rating is measured—you can read more about how thissystem works in our explanation of power supply efficiencyratings.) As the ratings improve, the efficiencies improve. Forexample, 80 Gold PSUs should provide 87 percent of the statedwattage at 20 percent load, 90 percent at 50 percent load, and 87percent at 100 percent load.This chart shows howmuch power is supposed to be provided at 20, 50, and 100 percentload for the various 80 Plus ratings.
Stick to 80 Plus, aka 80 Plus White, as the lowest rating worthconsidering. Step up from there based on the level of your buildand your budget. We recommend 80 Plus Bronze as a starting spot,since you can often get those models on sale for the same price asan 80 Plus alternative. You can move up to higher efficiencies tocompensate for the effect of hot climates or help keep electricitycosts down if your rates are high. But be aware that not all PSUmodels will hit their marks equally. For a clearer picture of whichcome out on top, look at the performance reports on the website ofthe group that issues 80 Plus certification.
Power supplies come in two flavors for how their power cablesattach: modular and non-modular. Modular power supplies havecompletely removable cables, while non-modular PSUs do not. Thecables on the latter are installed in a way that is fixed.
Predictably, modular power supplies cost more, but they have twoadvantages over non-modular models. First, you don't have to plugin all the cables, which reduces how much bulk to deal with inlimited space. Second, you can upgrade your PC's look by usingfancier, individually sleeved power cables, either as part of apre-made set sold by the same manufacturer (like Corsair offers) orfrom a third-party that specializes in selling such cables incustom lengths (like CableMod). Those cool, sleek-looking PCs yousee on Reddit and forums? They use individually sleeved cables.Some PSU manufacturerssell sleeved cable kits if you want to get fancy in your build. Youcan also buy these through third-party sellers.
Alaina Yee / IDG
One downside of modular power supplies is that you can easilylose track of cables if you don't plug them all in. Another, biggerconcern crops up if you build multiple PCs with modular powersupplies: Power cables for modular power supplies aren'tinterchangeable between brands, and sometimes not interchangeablebetween models from the same manufacturer either. Always checkbefore plugging in a set of cables that didn't come with your powersupply, lest you fry it by accident.
Non-modular power supplies have an inverse set of advantages anddisadvantages. Mostly you'll choose between these two types basedon several factors: your budget, the amount of space in your casefor spare cables or unused length, and your aestheticpriorities.An ATX power supply(left) next to an SFX power supply (right).
Alaina Yee / IDG
The size of your power supply matters for two reasons: It needsto be compatible with your case. And it affects how much physicalroom you'll have for the cables attached to it.
Make sure to buy an ATX power supply when your case supportsonly ATX power supplies, and SFX or SFX-L when your small formfactor case requires it. When you have a choice, you'll save moneyby choosing ATX, but you'll get more space to work with by choosingSFX or SFX-L. Should you want to reuse the PSU in another buildlater on, SFX or SFX-L power supplies can fit into an ATX spotusing an adapter bracket (like this one from SilverStone). Unfortunately, itcan't go the other way around.
The length of your power supply may matter, too. This is usuallyrelevant when you have a high-wattage power supply (usually over850W) in a compact case, or even a less beefy ATX power supply in asmall form factor case (under 20L). You can end up with not enoughroom for the power supply and storage of excess cable lengths.Selecting a compact ATX power supply (when applicable) and/orbuying custom-length cables can help.
Whenever possible, check the length of the power supplies you'reinterested in if you're planning a build with limited space. If notavailable on the product's webpage, contact the manufacturer orlook for reviews. Cross check the info you get against theclearance listed on your case's product page or in the manual.Power supplies withmore than one 12V rail usually list each one's output infoseparately (e.g., +12V1 and +12V2). This PSU has only one 12V rail,which is common these days.
Alaina Yee / IDG
The rails in a power supply are the individual wires that carrydifferent DC voltages—when the power from your home gets convertedfrom AC, your power supply splits them into 3.3V, 5V, and 12V DC.The components in your PC draw from those rails, with thepower-hungry parts like your processor and graphics card reliant on12V.
In the old days, you more often found power supplies withmultiple 12V rails. Such a feature allowed you to plug apower-hungry GPU (or multi-GPU setup) into separate rails, in orderto reduce the amount of heat a single wire has to endure. That inturn increased safety and preserved the longevity of the PSU.
These days, having multiple 12V rails in a PSU doesn't matter—not for the overwhelming majority of gaming PCs, anyway. Today'sgraphics cards don't draw as much power, and multi-GPU setups areall but dead. (The people rocking two RTX 3090s in a single PC arean extreme minority—and they know to look to the highest-end PSUsfor models that offer multiple 12V rails, anyway.) Pair that withthe fact that most power supplies sport a single 12V rail, and itbecomes a moot point.
If you're concerned about 12V rails because you heard it waspart of running two separate cables from your power supply to yourgraphics card, you can still use multiple cables. The benefit is areduction in heat going over those cables, which can be useful inhot climates. But as we explain in our article about using one power cable vs. two for a graphicscard, that's the only main benefit to expect.