A power supply might be labelled 300 W, 550 W or 1000 W. Until we know how much power the PC actually needs, that number tells us very little.
The simplest method is this:
- List your PC components, especially the processor and graphics card, but also the drives, memory, fans and cooling.
- Enter your configuration into a power consumption estimator, such as Newegg Power Supply Calculator or PCPartPicker.
- Leave some power headroom. Around 20–30% above the estimated maximum demand is a sensible starting point.
Newegg lets you include the CPU, motherboard, GPU, RAM and drives, among other components, and suggests a PSU wattage once you have entered your configuration. PCPartPicker also shows the estimated power requirements as you put together a build.
This is still an estimate. Only a measurement will reveal the actual power draw of a particular system, but the estimate is a perfectly adequate starting point for choosing the right wattage range.
Why leave headroom? Because choosing a power supply that only just meets your needs can come back to bite you. Keeping a reserve of ten to several dozen percent gives you more flexibility for brief power spikes and future upgrades.
There is no single wattage that suits every PC. A simple system without a powerful graphics card may need a few hundred watts, while a very powerful PC with a flagship GPU is in a different league altogether. For example, NVIDIA specifies 850 W as the required system power for the reference RTX 5080 and 1000 W for the RTX 5090. This shows why 850–1000 W makes sense for the most powerful builds, but is not a universal answer for every PC.
Does every power supply fit every PC?
No. A PSU can have exactly the right wattage and still be the wrong choice for a particular build. It might be too long, have the wrong cables or too few EPS connectors. That is why we check compatibility separately, rather than as an afterthought.
Two power supplies described as ATX do not necessarily have the same length. The width and height of this form factor are standardized, but the unit itself can be longer. In smaller cases, or when a drive cage sits directly in front of the PSU, a few centimeters can make a difference.
Then there are the cables. Modern graphics cards may need different connectors from older models, so you need to compare the GPU requirements with the PSU specifications before buying. Newer designs include connectors such as 12VHPWR and its successor, 12V-2x6.
Check the CPU power connections too. Some motherboards have more than one EPS 4+4-pin socket, and it is better to know this before buying than when everything is already laid out on your desk. A calculator will not help us here. It may add up the watts beautifully, but it will not check whether we actually have two EPS connectors for the motherboard or the right PSU cable for the GPU.
So if you are wondering how to match a power supply to your PC, do not stop at “650 W should be enough, it will probably work out.”
How do you calculate the PSU wattage you need?
If you are searching Google for “PC power supply calculator,” you are on the right track. You can calculate it manually, but tools such as Newegg Power Supply Calculator or PCPartPicker help you add up component requirements faster and get a useful reference point.
The processor and graphics card usually account for the largest share of power consumption. You also need to add the motherboard, RAM, drives, fans, liquid cooling pump, expansion cards and other devices powered by the PC.
There is a small catch here: TDP does not always mean the same thing as maximum power consumption. If the manufacturer lists a separate power limit, or you have reliable measurements from reviews, those are a better basis for your calculations.
Newegg lets you select individual components and uses them to suggest a PSU wattage. PCPartPicker works a little differently: as you put together your parts list, it continually displays Estimated Wattage, meaning the estimated power draw of the assembled system.
You can therefore use a simple formula:
CPU + GPU + other component power requirements + power headroom
However, do not treat this formula like a school equation where a result of 612 W automatically means buying a 650 W power supply. Components do not draw the same amount of power all the time, and the nature of their load changes. Graphics card manufacturers also usually base their recommendations on a specific test configuration.
When choosing wattage, it is therefore worth comparing three things: the calculator result, the GPU manufacturer's recommendation and the actual nature of your build. If you plan to replace the graphics card or processor later, additional headroom makes sense too.
For example, according to NVIDIA, the RTX 5080 has a total graphics power of 360 W, while the recommended PSU wattage is 850 W. For the RTX 5090, those figures are 575 W and 1000 W respectively.
That also answers the question “what PSU wattage does my PC need?” The answer depends on the specific build. 750 W is not always “a lot,” and 1000 W is not always excessive.
How do you recognize a high-quality power supply?
“850 W” on the label alone tells us very little. A power supply can have the right wattage and still be a model we would not want to connect to an expensive GPU.
For years, 80 PLUS® certification was the most recognizable marking on power supplies. It is still very useful information, of course, but stopping there is like judging a monitor solely by its refresh rate. We know something important, but we still do not know everything.
80 PLUS® primarily classifies power supplies by energy efficiency at specific load levels. Bronze, Silver, Gold, Platinum and Titanium therefore tell us a lot about efficiency, but do not constitute a complete quality assessment of the entire PSU.
That is why it is worth looking at tests and certifications from Cybenetics too. ETA provides a much broader picture of efficiency under different load conditions, while LAMBDA assesses noise performance. It simply gives us more data on how a power supply behaves in practice.
The ETA program tests efficiency under more than 1450 load combinations, which can produce around 25,000 measurement points after interpolation. Tests also record voltages, ripple, power factor, temperature and noise, among other parameters. Like 80 PLUS®, Cybenetics awards “metal” certifications such as Gold or Platinum based on the results.
Then there are the protections:
- OVP – over voltage protection – protection against excessively high voltage,
- UVP – under voltage protection – protection against excessively low voltage,
- OPP – over power protection – protection against overload,
- OCP – over current protection – protection against excessive current,
- SIP – surge and inrush protection – protection against voltage surges and inrush current,
- SCP – short circuit protection – protection against short circuits,
- OTP – over temperature protection – protection against overheating.
These are not decorative abbreviations to fill a product specifications table. They are mechanisms designed to limit operation or shut down the power supply in a dangerous situation, protecting against damage.
For newer, more power-hungry GPUs, check whether the power supply complies with the newer ATX 3.0 or 3.1 standards. These specifications account for brief power spikes, so the PSU is designed to handle the very high loads generated by next-generation graphics cards (which you probably will not even find listed in their specifications).
That does not mean an older PSU automatically belongs in the bin. It all depends on the specific build and the unit's specifications. However, if we are building a new PC with a powerful graphics card, compliance with a newer standard is simply a sensible starting point.
Newer designs also offer native 12VHPWR or 12V-2x6 cables. An adapter is not automatically the root of all evil, but if we can power the card with a native cable from a suitable PSU, why add another piece to the puzzle?
If a power supply looks great on paper but nobody has properly tested it, blind faith earns us no extra points. We look for measurements: voltages, ripple, temperatures, behavior under load and noise levels.
If you value quiet operation, check how the fan behaves too. In some models, it stops completely at low load. And yes, a fan that is “not running” can be a desirable feature rather than a reason to panic.
How do you choose a PSU form factor for your PC case?
Check the case specifications first, then choose the power supply. That order saves a lot of frustration.
ATX is the most common form factor in desktop PCs. Standard ATX power supplies are around 150 mm wide and 86 mm high, but their length can vary depending on the design. That is why “maximum PSU length” in the case specifications is not just a formality.
Smaller PCs may use SFX. A typical SFX unit measures 125×63.5×100 mm, taking up much less space than a conventional ATX PSU. There is also SFX-L, a form factor similar to SFX but with a longer enclosure. More specialized compact builds may also use TFX.
Simply saying “my case supports ATX” does not settle the matter. You need to check the maximum PSU length, the space available for routing cables and whether a drive cage or other components take up some of that space.
There is another detail that tends to make itself known only when you start assembling the PC: cable length. In a large case, being a few centimeters short on the 24-pin or EPS cable can easily derail your weekend gaming plans.
This applies to modular models too: detachable cables help keep things tidy, but the sockets and plugs themselves also need space. A three-centimeter difference sounds harmless until you try to fit the cables and a drive cage alongside them.
So if you are wondering which power supply to choose for a desktop PC, checking the form factor takes less than a minute. Trying to install a PSU that turns out to be a few centimeters too long will take considerably longer.
How do you choose a power supply for your PC?
The wattage is calculated, the dimensions fit and the cables check out. What remains is to check whether the power supply itself is a design we actually want in this PC.
Compare the calculator result with the GPU manufacturer's recommendation and leave some headroom. Check the form factor, PSU length, cables and connectors, including the EPS connections for the CPU. With a powerful new graphics card, also verify the ATX standard and how the card receives power.
Next come certifications, protections and independent tests of the specific model. Only then can you comfortably compare things such as modular cabling, warranty length, semi-passive operation or price.
Which brand of PC power supply should you choose? The brand alone is not everything: the specific model and its test results matter. But since you are asking us, we obviously have a favorite. You probably know it: it is called ENDORFY. ;)
On a more serious note, we work through the same checklist. Wattage, connectors, form factor, protections and the nature of the build come first.
How much does a good PC power supply cost?
There is no single threshold beyond which a power supply suddenly becomes “good.” The price rises with wattage, design quality, efficiency, cabling and features intended for newer hardware. Warranty and noise performance also play a part.
The ENDORFY portfolio makes the different budget levels easy to illustrate. Elementum sits at the most affordable end, followed by Vero, then Enduro and finally Supremo. This is not a ranking from “poor” to “good” to “best,” but different answers to different needs and budgets.
So rather than asking “how much does a good power supply cost?”, it is better to ask “how much does the right power supply for my PC cost?” The difference may seem small, but it can prevent plenty of pointless purchases.
There is no point buying a huge unit for a simpler build just because it looks more “future-proof.” On the other hand, saving a few dozen zlotys on a PSU that will power an expensive graphics card and a powerful processor can prove costly later.
In practice, setting a budget only makes sense once you know what you are looking for. Otherwise, it is easy to “save” 50 zł on a PSU for a graphics card costing several thousand, or buy a 1000 W unit for a PC that will never come close to using half that power. Either choice earns you little more than an achievement for a purchase you have not quite thought through.
