Protect A PC With An Uninterruptible Power Supply

An Uninterruptible Power Supply (UPS) provides emergency power when the utility mains electric fails. It is typically used to maintain stable power to (keep switched on) a PC and monitor when there is a power cut or other mains electricity issue – and may be used to keep other devices on too e.g. a wireless router or external hard drive for backups.

Can Power Cuts or Surges Damage My PC? Yes they can. Three problems affecting the mains utility power supply can possibly damage your computer:

1. Power Cut – all power goes off suddenly (even if only for a second or two) so your PC and peripherals switch off immediately. At best, you will lose any open documents/emails etc that you had not saved before the cut. At worst, a sudden loss of power can cause Windows to become corrupted (so it won’t restart) or possibly cause physical damage to the hard drive in the PC (‘scratches’ are caused on the drive surface which may stop Windows loading or destroy some of the files on the hard drive).

2. Power Surge (or spike) – an increase in mains voltage which may damage sensitive electrical components – like those inside a PC (motherboard, hard drive, memory etc). Such damage may destroy the PC component or shorten its lifespan considerably, so your PC fails sooner.

In theory, the power supply inside your PC should offer some protection but it may be damaged (‘blown’) itself by the surge and therefore let the surge through to damage the rest of the PC components. In our computer repair business we come across cheap power supplies that let surges through as they blow which then go on to destroy the motherboard as well.

3. Brownout (or ‘dirty’ power) – a drop in mains voltage, typically indicated by lights in the house dimming or flickering. Such voltage drops may cause your PC or peripherals to freeze or shut down immediately (even if other devices stay on). The potential damage caused to your PC is the same as for Power Cut in point 1 above.

How Can A UPS Help? Think of a UPS as like a very big laptop battery for a PC – even when the mains electricity is cut off/interrupted, the battery inside the UPS will continue to keep the PC going for a while – giving you time to finish working, save your documents and then shut down the PC normally (if the mains electricity has not already come back on).

A good UPS comes with software and a USB cable that lets you set up the UPS to automatically shut down your PC ‘nicely’ (i.e. in the normal way) before the UPS battery runs out even if you are not there. The UPS battery normally provides computer use for 10 to 30 minutes, depending on the power output of the UPS and how many devices you have connected to it.

UPS also regulates the electricity from the mains utility so that surges or brownouts are removed before they reach you and the voltage to your PC is kept at a constant rate so it is unaffected.

What Features Do I Need In A UPS?

Number of Sockets: A typical UPS aimed at home/SOHO users may have up to 10 sockets that you can plug equipment into. Usually half of them will be simple surge protected sockets (like you find on a surge protected extension cable) that you can use for things like printers and scanners that don’t have to be kept on.

But the other half of the sockets will be covered by the UPS battery i.e. they regulate a constant power source and keep connected equipment like a PC/monitor turned on even if the mains electricity is cut, interrupted or the mains voltage surges or drops. Choose a UPS with as many sockets as you need but remember that half of them may be surge protected only, not UPS battery powered.

Software: As mentioned above, the ability to set the UPS (via software and USB cable) to turn off the PC automatically before the UPS battery runs out is very useful – because you might not be there to shut down the PC yourself. Software may also let you set a sound alarm where the UPS beeps loudly if the electricity has gone off and it is running on the battery.

Power Output: UPS have different outputs that determine how long the battery can keep equipment like a PC turned on when there is a power cut/issue. The higher the rated output, the longer the time available to run off the battery – and the higher the price.

UPS specifications love to highlight Volts as a very high number but this is not what is important for computers. You need to look at the Watts (W) it can provide to determine if it is sufficient for your PC and peripherals. Generally speaking, a good quality UPS like a 330W / 600VA APC model is sufficient for a decent PC, a modern LCD (flat screen) monitor, wireless router and printer/scanner.

If you have an expensive high spec PC (particularly a Gaming PC with high end graphics card) or multiple external hard drives to keep going you may need to consider a UPS with a higher wattage. E.g. a 330W UPS may not work with a PC that has a 700W internal power supply because the PC needs more power than the UPS is capable of passing through.

Tip: To find out the Watts of the power supply in your computer, check the manufacturer’s website or take the side of your PC off and look on the supply itself – it is usually written on the side of the supply e.g. 300W = 300 watts).


UPS is not sexy but it is like insurance for your PC and makes as good sense as taking regular backups of your documents in case of hard drive failure – which hopefully you already do… UPS is even more important if you regularly suffer power interruptions (particularly common in rural areas).

2 thoughts on “Protect A PC With An Uninterruptible Power Supply”

  1. I have a surge protected power strip but not a ups – if its that important why dont offices use them for each computer?

    • 3 possible reasons Cathleen which shouldn’t stop you thinking of UPS for yourself:

      1) in a very small business they may not know about UPS or understand/care about the risks. Or they don’t want to spend any money/time on IT – we come across small businesses who don’t even bother backing up their data, never mind protecting individual PCs!

      2) a very large business may have regulated power and a backup generator fed through to each individual office so individual UPS may not be required (and they are also covered by point 3 below)

      3) all but the smallest offices store user documents and emails etc on a server (and also back them up) – you can bet your bottom dollar that the server will have a UPS! So if a PC does goes down they haven’t lost any data. Worst case, they just reinstall Windows which is typically a lot easier on an office PC than on a home PC (which is likely to have lots more different programs and individual settings tailored to how you like it)

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