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 your
build, then go hunting for specific models that fulfill those
criteria. We've listed and explained them below, in the order of
most important to least important for gaming builds. Some of these
relate to practical concerns, like having enough power, but others
take into account aesthetics as well.
> Not building a gaming PC? You may find our general advice on buying a power supply more
A power supply's number one job is to provide enough power for a
PC's components, no matter what type of computer you're building.
But calculating that number takes a bit more math than looking up
the TDP (thermal design power) spec for each component, adding up
those wattage numbers, and then buying a PSU close to the
You need more wattage than that. A surplus, commonly called
headroom, allows your power supply to run at peak efficiency. It
also gives you the ability to add parts or upgrade to components
with higher power requirements (or both), depending on the amount
of headroom you go for.
This 750W power supply
is 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 your
current budget and your future upgrade plans. Your baseline will be
a range of 40 to 80 percent of the wattage rating—you should stick
within those boundaries for peak efficiency. Pick the lower end of
that if you intend to overhaul your rig with a much beefier CPU-GPU
combo down the road and don't want to buy a new power supply to
accommodate those changes. (This strategy works best if you plan to
do those updates within the PSU's warranty period.) Choose the
higher end if you don't plan to do power-hungry upgrades or reuse
the PSU in a new build with more powerful hardware.
An old-school rule of thumb is to aim for 50 to 60 percent use
of the wattage rating. You'll have plenty of room for upgrades, and
you won't have to worry about the effect of ambient temperatures on
actual amount of power available. Many modern builders don't like
such a large buffer, though, citing improved power efficiency in
PSUs (see below). Neither attitude is inherently
wrong. It doesn't hurt to be closer to 40 percent usage than 80
percent—you won't draw more power at the wall with a higher wattage
PSU. That's based on what your components actually pull, not the
wattage rating. But you can end up overspending on something you
don't make full use of.
power supply calculator can help you calculate your wattage needs.
If you use Outervision's popular online calculator to do all
this math for you, you'll encounter the modern attitude. For more
headroom, simply go for a power supply with a higher wattage. We
suggest padding the headroom when working with cheaper power
supplies or living in an area with hot weather.
Here's how this shakes out in a concrete example: After doing
the math yourself (or consulting an online calculator), you find
out your system's total draw is 300W. If you're on a budget with
modest hardware, you could buy a cheaper 500W power supply, like
the EVGA 500 W1. Got a little more cash? You can
also go up to a 750W power supply, like the Cooler Master Masterwatt 750, and ensure that
you'll have the power needed for a later jump up to a high-end
graphics card. (You know, when they're widely available again.)
Number of cables
The more cables you
have available, the more flexibilty you have for your build. (But
the more room you need, too.)
Alaina Yee / IDG
Usually the lower the wattage of a power supply, the fewer power
cables it has. Go low enough and this point is a bit moot—g
enerally, systems requiring a 400W or lower PSU just don't have
enough components to need a ton of power cables. Cost also
influences the number of cables. Pricier models generally offer
You have to be most attentive to this point when attempting to
cram a bunch of parts into a PC while also not spending a lot on a
power supply. Go too low and you just won't have enough cables for
everything you plan to put in your system. Sure, maybe your wattage
requirements are met, but imagine this scenario: Your graphics card
and sound card both require additional power, but sit at a wide
distance from each other on the motherboard. If you only have one
PCIe cable, you're going to be in a bind. (Plus, it's not ideal
running those on the same cable anyway.) This example is for a
lower-end build, but you can encounter this issue in higher-end
Avoid this problem by going over your list of parts and tallying
how many cables of each type you'll need. Factor in any future
upgrades you're anticipating, too—for example, going from a
graphics card with a single 6- or 8-pin connector to one with two
power connectors. You can run a graphics card on one cable, but if
you live in a warm climate, it may be optimal to use two separate
cables for each connector to reduce the risk of the cables
You can see the difference for yourself by comparing several
PSUs. For example, the Cooler Master MWE Bronze 500 offers just five
cables: one each for ATX 24-pin (motherboard), EPS 8-pin (CPU),
Molex (fans/accessories), SATA (storage/optical drives), and PCIe
6+2 (GPU/expansion cards). Go up in wattage to the Cooler Master MWE White 550, and you get an
additional SATA and PCIe cable. But increasing wattage doesn't
guarantee more cables—the dirt-cheap EVGA 500 N1 has just one PCIe cable (and a
piddly two-year warranty).
Power supply efficiency tells you how much actual power you can
expect to get from a power supply. While the wattage tells you the
theoretical amount provided, the power efficiency rating indicates
how much power you should expect to have after losing some to heat
and other causes.
These days most everything is 80 Plus-rated or higher. At
minimum, these power supplies provide 80 percent of its advertised
wattage at 20-, 50-, and 100-percent load. (That's the metric by
which the rating is measured—you can read more about how this
system works in our explanation of power supply efficiency
ratings.) As the ratings improve, the efficiencies improve. For
example, 80 Gold PSUs should provide 87 percent of the stated
wattage at 20 percent load, 90 percent at 50 percent load, and 87
percent at 100 percent load.
This chart shows how
much power is supposed to be provided at 20, 50, and 100 percent
load for the various 80 Plus ratings.
Stick to 80 Plus, aka 80 Plus White, as the lowest rating worth
considering. Step up from there based on the level of your build
and your budget. We recommend 80 Plus Bronze as a starting spot,
since you can often get those models on sale for the same price as
an 80 Plus alternative. You can move up to higher efficiencies to
compensate for the effect of hot climates or help keep electricity
costs down if your rates are high. But be aware that not all PSU
models will hit their marks equally. For a clearer picture of which
come out on top, look at the performance reports on the website of
the group that issues 80 Plus certification.
Modular vs. non modular
Power supplies come in two flavors for how their power cables
attach: modular and non-modular. Modular power supplies have
completely removable cables, while non-modular PSUs do not. The
cables on the latter are installed in a way that is fixed.
Predictably, modular power supplies cost more, but they have two
advantages over non-modular models. First, you don't have to plug
in all the cables, which reduces how much bulk to deal with in
limited space. Second, you can upgrade your PC's look by using
fancier, individually sleeved power cables, either as part of a
pre-made set sold by the same manufacturer (like Corsair offers) or
from a third-party that specializes in selling such cables in
custom lengths (like CableMod). Those cool, sleek-looking PCs you
see on Reddit and forums? They use individually sleeved cables.
Some PSU manufacturers
sell sleeved cable kits if you want to get fancy in your build. You
can also buy these through third-party sellers.
Alaina Yee / IDG
One downside of modular power supplies is that you can easily
lose track of cables if you don't plug them all in. Another, bigger
concern crops up if you build multiple PCs with modular power
supplies: Power cables for modular power supplies aren't
interchangeable between brands, and sometimes not interchangeable
between models from the same manufacturer either. Always check
before plugging in a set of cables that didn't come with your power
supply, lest you fry it by accident.
Non-modular power supplies have an inverse set of advantages and
disadvantages. Mostly you'll choose between these two types based
on several factors: your budget, the amount of space in your case
for spare cables or unused length, and your aesthetic
Form factor and dimensions
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 needs
to be compatible with your case. And it affects how much physical
room you'll have for the cables attached to it.
Make sure to buy an ATX power supply when your case supports
only ATX power supplies, and SFX or SFX-L when your small form
factor case requires it. When you have a choice, you'll save money
by choosing ATX, but you'll get more space to work with by choosing
SFX or SFX-L. Should you want to reuse the PSU in another build
later on, SFX or SFX-L power supplies can fit into an ATX spot
using an adapter bracket (like this one from SilverStone). Unfortunately, it
can't go the other way around.
The length of your power supply may matter, too. This is usually
relevant when you have a high-wattage power supply (usually over
850W) in a compact case, or even a less beefy ATX power supply in a
small form factor case (under 20L). You can end up with not enough
room for the power supply and storage of excess cable lengths.
Selecting a compact ATX power supply (when applicable) and/or
buying custom-length cables can help.
Whenever possible, check the length of the power supplies you're
interested in if you're planning a build with limited space. If not
available on the product's webpage, contact the manufacturer or
look for reviews. Cross check the info you get against the
clearance listed on your case's product page or in the manual.
Power supplies with
more than one 12V rail usually list each one's output info
separately (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 carry
different DC voltages—when the power from your home gets converted
from AC, your power supply splits them into 3.3V, 5V, and 12V DC.
The components in your PC draw from those rails, with the
power-hungry parts like your processor and graphics card reliant on
In the old days, you more often found power supplies with
multiple 12V rails. Such a feature allowed you to plug a
power-hungry GPU (or multi-GPU setup) into separate rails, in order
to reduce the amount of heat a single wire has to endure. That in
turn increased safety and preserved the longevity of the PSU.
These days, having multiple 12V rails in a PSU doesn't matter—n
ot for the overwhelming majority of gaming PCs, anyway. Today's
graphics cards don't draw as much power, and multi-GPU setups are
all but dead. (The people rocking two RTX 3090s in a single PC are
an extreme minority—and they know to look to the highest-end PSUs
for models that offer multiple 12V rails, anyway.) Pair that with
the fact that most power supplies sport a single 12V rail, and it
becomes a moot point.
If you're concerned about 12V rails because you heard it was
part of running two separate cables from your power supply to your
graphics card, you can still use multiple cables. The benefit is a
reduction in heat going over those cables, which can be useful in
hot climates. But as we explain in our article about using one power cable vs. two for a graphics
card, that's the only main benefit to expect.