There’s more to getting the right power supply than just picking the one with the highest number
Power supply units (PSUs) are an essential component of any computer for what should be fairly obvious reasons. Most of us don’t waste a second thought on our power supplies for the majority of the time we use our PCs, but when the time comes to buy a new one, you’ll find that PSUs are as complex and varied as any other computer component and just as deserving of the proper attention.
In case you suddenly find yourself thrust into a potentially confusing world of wattages, efficiencies, amps, volts and rails, we’re here to help. But fair warning: if you’re not building a performance or gaming system, some of this information will be of no practical value. If you are, though, it’s required knowledge. Either way, you might find it useful to know.
What To Look For
The most basic thing you need to know about PSUs is that they all have a wattage rating, which tells you how much power they can deliver to your system. All components in a system draw a certain amount of wattage, which is taken from the total available. A hard drive might need around 15 to 30W, and a graphics card might need as much as 300W at its peak. If all of the components in your system add up to more than the maximum wattage of your PSU, it won’t function, and you’ll have to install a more powerful one.
At least, that’s the basic version of that information. This is where things get a little tricky, because not all PSUs are created equal. All PSUs are, to some extent, inefficient. This means that some proportion of their wattage is converted into heat energy before it can power anything. Some particularly cheap PSUs have been reported as losing up to 150 to 200W of their capacity to heat, meaning that the 600W rating might actually only provide a 400W supply.
As a result, you need to make sure that your PSU has a decent overhead compared to what you actually need. You can check using online power calculators what the rough draw of your system’s configuration is, and then you should buy a PSU with a big enough overhead to account for the base inefficiency and the gradual aging of the components, which will also reduce its capacity to deliver power. PSUs are usually engineered to work best at around 60% capacity, so use that value as your target.
Annoyingly, it’s hard to know what a PSU’s efficiency is like without testing it, so the good news is that there’s a certification system set up, which will tell you quite how efficient a PSU is. The 80 Plus certification ensures that a PSU is delivering at least 80% of its wattage as usable power, and various tiers of award through bronze, silver, gold, platinum and titanium can ensure that your PSU is anything up to 90% efficient in all circumstances. Look for the logo on the box!
You should also take care to check that a power supply has the right connections. Most come with adaptors to help you choose the right configuration of plugs based on the varying technologies in your system (e.g. Molex three-pin, Molex fourpin, SATA, etc.), but if you have a highend graphics card that requires a separate power supply, make sure you also have the six- and eight-pin connections they need to draw power!
So-called ‘modular’ PSUs allow you to plug in only the cables you need at any given time (in most PSUs, unused cables simply hang loose). Modular PSUs mean more space to manoeuvre inside your case, but they also mean greater air flow and thus, you could argue, translate to a slight performance increase. You’ll pay extra for the technology, but it’s really down to personal preference whether you want it. It might sway a decision, but there’s no reason to base one on its inclusion.
If you see ‘DSP’ mentioned, this stands for ‘Digital Signal Processor’, a technology which ensures that power is ‘clean’, which is to say delivered consistently, leading to a more reliable supply of power and thus a more stable system. It’s probably only relevant to those overclocking their systems who have very tight margins for error, but it’s worth knowing about just in case.
Pricing
Consumer-oriented PSUs cover a rather insane price range, starting at about £10-£15 for the cheapest and topping out at a borderline-ludicrous £250. It goes without saying that the cheap models should be avoided except for the most basic, shortterm computing. It’s simply not worth the risk to your components to run on one.
However, you can find good-quality 500W power supplies as low as £35. They’ll be short on extras and may have trouble if paired with the highest-end graphics cards and can’t really be used in SLI/CrossFireX systems, but for non-gaming machines they should more than suffice. If you’re spending more than £50 and don’t have a powerful graphics card or other high-power component, ask yourself why.
If you are building a gaming system, though, we’d recommend budgeting £60 to £80 for a PSU. At this price, gaming PSUs come with things like lighting accessories and high efficiency ratings. You may want to spend more for extras like modular designs or ultra-quiet fans, but once you go beyond this range, you’re firmly into enthusiast territory – at which point, the sky’s the limit!
Specific Models
If you’re looking for a PSU, we’d recommend the following hardware:
Corsair V2 CX Series (£34)
This 430W 80 Plus Bronze-rated PSU is ideal for any low-to-medium power system. With a 32 amp 12V rail, 120mm silent cooling fan and master power switch, it has everything the PC-building enthusiast needs at a price that’s neither worryingly cheap or upsettingly expensive.
EVGA Supernova NEX650G (£75)
Rated 80 Plus Gold, this 650W PSU has a 53 amp 12V rail, 135mm silent fan and four PCIe connectors, so it’s perfect for multi-card and high-demand systems. It’s expensive, but not unreasonably so for a modular system with these capabilities.
Coolermaster Vanguard (£160)
PSU prices can quickly get crazy, but sometimes that’s exactly what you want. This fully modular 1000W PSU has eight PCIe connectors, a 135mm fan and a 12V rail capable of reaching 83 amps, so there’s no doubt that it’s got some serious chops. Do you need it? Well, maybe not. But if you have the money burning a hole in your pocket…