6 Things to Know When Buying a Power Supply Unit (PSU)
When you are assembling a new computer, don’t give in to the temptation of buying a cheap power supply unit (PSU). The PSU supplies power to your entire system, and a bad one can cause that expensive motherboard or graphics card to malfunction. Don’t take this risk, ever!
PSUs don’t have the same marketing or glitz value as graphics cards or processors. You know that you want Intel’s new Skylake CPUs and you’ll endlessly debate Nvidia vs. Radeon, but chances are, you’d go with just about any PSU, right? That’s a mistake — one that will cost you big time.
That’s not to say that you need an expensive PSU. There are budget models available, which fit the idea that it’s cheaper to build your own PC. But you need to know what to look for. So here’s a quick guide to selecting the right PSU without breaking the bank.
1. Continuous Wattage > Peak Wattage
Wattage is the base number to help you distinguish which PSU you need and how it is rated. Simply put, this is the total amount of watts the PSU can deliver to the different parts of your PC. You’ll find models that provide 300W and some that go all the way up to 1200W.
While models will advertise this number proudly on the box, it might not tell you the full story. For example’s sake, consider a hypothetical 500W PSU. If it means Continuous Wattage, that’s great. If it’s the Peak Wattage, you might want to avoid it. You can usually check which it is on the model’s specifications page.
Continuous Wattage and Peak Wattage are ratings based on tests by the manufacturer. Continuous Wattage indicates that it can deliver those 500W continuously without fluctuations. Peak Wattage indicates 500W is the maximum power it can deliver, but probably only for a minute before dropping down.
In simple buyer terms, look for continuous wattage ratings, ignore peak wattage ratings, and ignore a product that doesn’t advertise its continuous wattage rating. If you can’t tell which one it is, don’t take your chances and just move on.
2. How Many Watts Do You Need?
Not all PCs are built alike, so the amount of power each one needs is different. A high-end gaming PC is obviously going to need more watts to run than a simple home office PC. But how do you calculate the amount you actually need?
The Internet is full of simple calculators that will do the job for you. Try Outervision’s Extreme Power Supply Calculator or Cooler Master’s Power Supply Calculator. If you know what you’re doing, Cooler Master’s version is better, but if you’re not sure about what parts the calculator is asking for, stick to Outervision’s basic calculator.
Both calculators will give you a certain idea of how much wattage you need, and depending on how you entered your information, feel free to round it up to the closest PSU.
In fact, you could even go two rungs higher. For example, if the calculator says you need 370W, then a 400W PSU should be fine but 500W wouldn’t be bad either — especially if you plan on adding more parts to the rig eventually.
3. Save Energy With Efficient PSUs
Our social responsibility to the planet compels us to not consume more resources than we need to, so get a PSU that is as efficient as possible! Even if you don’t care about the planet, an efficient PSU will still save you big bucks on your energy bill.
So what is efficiency in a PSU? Well, your PSU is taking AC power from the outlet and converting it to DC power, which is then sent to all the parts — but typically the PSU wastes some energy in the conversion process. Therefore, PSU efficiency is about how much it can convert and how little it wastes.
Therefore, an 80% efficiency indicates it’s able to convert 80% of the AC power to DC while 50% efficiency indicates it converts 50% of the AC power to DC. In even simpler terms: a higher efficiency percentage is better and will require less power from the outlet.
The most efficient PSUs are the ones that come with an 80 Plus rating, which is assigned by an independent certifier. Even in 80 Plus PSUs, there are different levels: 80 Plus, 80 Plus Bronze, 80 Plus Silver, 80 Plus Gold, 80 Plus Platinum, 80 Plus Titanium. (These are ordered from worst to best.)
An additional advantage of these efficient PSUs is that they generate far less heat than other PSUs, and usually run at quieter volumes too. Manufacturers will advertise 80 Plus certified PSUs proudly, but in case you’re having trouble finding information, check the full list of 80 Plus PSUs.
4. Details You Can Safely Ignore
Everything up to now has just been about the bare basics of PSUs. As with any technology, you can geek out and get a lot more specific about what you want or need, but if you are a beginner, the aforementioned three aspects will matter the most to you in your buying decision.
That being said, there’s some other jargon you might encounter while shopping for a PSU. You can safely ignore all of this until you’re more familiar with PSUs in general, but if you’re curious about what they mean, here are some specs you might see.
- Rails: You can get multi-rail or single-rail PSUs. Both have their pros and cons and you don’t need to worry about the technicalities right now. If you live in an area where power fluctuations or outages are normal, then you should consider multi-rail. For any other scenario, or if you use a good uninterruptible power supply (UPS) , then just get a single-rail PSU.
- Voltage Stability: If you’re ticking all of the above boxes, then voltage stability won’t be an issue. This basically refers to the PSU’s ability to keep supplying power at 12V without dropping.
- Cabling or Connectors: Unless you’re buying a high-end specialized PSU, you should be fine with the cabling that comes in the box. High-end PSUs do offer something called “modular cabling”, which lets you fit custom cables and pin connectors to attach your parts to it. Not important for the average user.
- AT vs. ATX: Some PSUs are made for AT-type motherboards, others for ATX-type, and some for both. Chances are, you’re using a standard ATX motherboard and will need a standard ATX PSU, but you may want to double check your motherboard’s details just in case.
- Repair Units and Accessories: No, you don’t need a wattage tester or guides on how to fix a PSU. If you diagnose a problem with the PSU , your only option is to replace it — and hope that it’s still under warranty.
5. Why You Shouldn’t Cheap Out
So why are we harping on about buying a quality PSU instead of just going with whatever came bundled with your PC case or a relatively unknown brand’s models? Well, like we said at the start, your PSU affects every part in your computer system and can end up frying circuits in the case of a power fluctuation.
But apart from that, quality PSUs have other benefits that make them worthwhile. Here are a few:
- They last a long time. No, really. Chances are that if you buy a quality PSU right now, rated about 100W to 200W higher than what you currently need, then you’ll be able to use it for your next PC upgrade as well. At the very least, it’ll last you several years.
- They have resale value! Upgrading to a new PSU? You’ll find buyers for your old one on Craigslist and Ebay. Heck, you could even repurpose it as a bench power supply for DIY projects.
- Standardized sizes let you get creative with old PSUs too. Since all PSUs are generally shaped the same, just find a simple case and you can make yourself a cool and quiet HTPC .
6. Where to Find Reliable Reviews
Manufacturers release new PSU models at a quick rate, and it’s a relatively niche computer part for tech reviewers. Here are a few well-known and reputable brands to start you off: Corsair, Cooler Master, Antec, Be Quiet, Seasonic, and XFX. These aren’t the only ones, of course.
Once you’ve gone through the aforementioned steps, you should have a fair idea of how many watts you need, which trusted brand models are certified 80 Plus for that wattage, and what fits in your budget. Now it’s time to actually do some research.
Jonny Guru is considered one of the most reliable Internet voices for advice on PSUs. You can search for your product on JonnyGuru.com, check out the JonnyGuru Forums to find help, or rely on his legendary PSU Tier List to find the right model for you.
As for other general tech sites, Tom’s Hardware and AnandTech are renowned for their in-depth PSU reviews and are known to have knowledgeable commenters who will share extra information and their own experiences. Again, both sites have forums with an active community of helpers.
Also, remember to take a look at our own roundup of the best PSUs for PC builders . And finally, if you need to people to talk to, head over to /r/BuildAPC on Reddit to find out which PSUs people are leaning towards these days.
Have Any Questions on PSUs?
With PSU brands, personal experiences add a lot of value. So tell us which power supply unit you’ve currently got and which brands have earned or lost your trust. I’ve personally shifted from Corsair to Cooler Master and found that CM has been much more reliable.
Hope this helped! If you have any further questions, ask down below and we’ll try to help you. Are there any other tips we missed? Share them with us down below, too!
And if you’re looking to buy a UPS to go with your PSU, here are the best UPS units you can buy .