Part 6: Choosing a power supply (PSU) and case cooling

In this series of articles, I will be giving my opinions on the best ways to get started in building your own computer. I’m going to go into detail about how you can select the right components for you.

We’ve already looked at why you might build your own computer and what all the parts actually do, as well as chosen a number of parts already. Now let’s complete the part selection process with the case cooling and power supply options.

1. Introduction to PC building
2. Choosing a processor (CPU) and motherboard
3. Choosing a case, memory (RAM) and cooler
4. Choosing a graphics card (GPU)
5. Choosing storage and operating system
6. Choosing a power supply (PSU) and case cooling
7. Tips for actually assembling your computer
8. Example build – The “cheapest (good)” build your own PC in Spring 2022
9. Example build – The “making your money go furthest” build your own PC in Spring 2022
10. Example build – The best “high-end enthusiast” build your own PC in Spring 2022

Case fans

These are really important and often overlooked. The more fans you have, the more fresh air is sucked into your case, passes over the components to cool them and is expelled out again. However, fans are one of the main sources of noise for your computer, so more fans usually means more noise. Smaller fans tend to be noisier than larger fans and do not move as much air, so it makes sense to fit the largest fans your case can support.

You will need to know how many (if any) fans your case comes with and how many places there are to mount them. If you chose an AIO cooler earlier on, be aware that the AIO has a radiator which will need to be mounted in one of these locations.

Finally (and importantly), you need to plan for the way you want air to flow through your case. There is no point having all fans point inwards into your case to get cold air in from all directions, because once inside, the air will become turbulent with no clear path or exit point. You must have a clear idea as to where the cold air will come from and how it will leave the case. It is also worth remembering that hot air rises, which is what it will do inside your case.

As a general rule of thumb, I recommend that you draw cold air in from the front and bottom of the case and exhaust it through the rear and top of the case. Many cases are set up to follow this commonly used system. Once you have built your computer, don’t locate it directly on the floor, particularly if you have carpet. Dust and blockages are likely to occur, eventually causing your components to overheat and suffer performance drops or even fail completely.

Read reviews of case fans to discover the best, quietest, largest fans your case can accommodate while staying within your budget. Noctua are renowned for their quiet, excellent fans but they do come at a price – £13 for a 12mm fan at the time of writing. I have Arctic P12s in my computer (£10 on Amazon but can be found for as little as £4 elsewhere) and I find them excellent – quiet and efficient, and the savings meant I could concentrate my budget elsewhere while ensuring my computer has adequate cooling.

When buying fans, you should look for PWM fans as your computer will be able to precisely control the fan speed for you. And if you are interested in RGB lighting, fans are typically one of the best ways to light up your system, although expect to pay more for RGB lit fans compared to standard ones.

Power Supply (PSU)

I’ve saved this one until last for a very good reason. Don’t cheap out on your power supply. Your power supply takes the raw power from the mains and precisely converts it into the power needed by your delicate components. A cheap power supply will do this cheaply. A good quality power supply will do this in a good quality way. Don’t spend £800 on components and then fry them all with a £20 power supply.

There are a few things to consider when choosing a power supply:

• Power: How much power will your computer need? This is critical – if your power supply can not provide enough power, your computer will not be stable or may not even start at all. Typically, PSUs start at about 300W but can go to well over 1000W. Remember, just because a PSU is rated for 750W, that doesn’t mean that’s how much it will draw all the time. That is simply how much it can provide if it is needed. Computers running low-powered applications such as Word or Excel may typically run at under a tenth of that, depending on the components involved.
  • In order to get the right PSU, I recommend using a PSU calculator to work out how much power your computer needs. More power means a more expensive PSU.
  • A GPU uses more power than anything else in your system. Factor this in.
• Physical Size: Will a standard ATX power supply fit in your case, or do you need a different size? Check your case manufacturer’s website. Standard ATX power supplies tend to be cheaper.
• Modular or fixed cable: Modular means you can remove cables you are not using, which is much neater. Semi-modular means you can remove some of the cables you are not using. Fixed means all the cables you might possibly need are hard wired into the PSU, meaning they can never be removed and will still take up room in your case even if you don’t need to use them. Naturally, modular power supplies are usually more expensive.
  • Don’t ever try to cut power supply cables or open up a power supply, even if the power is off. Ever.
• Efficiency: Power supplies can be rated as 80+, Bronze, Silver, Gold, Platinum or Titanuim. Some of the power your PSU takes from the wall will be lost as heat. For example, if your PSU is 80% efficient, it means that 20% of the power it takes from your home electricity supply will be wasted. If it takes 500W from the wall, the computer will use 400W and 100W will be wasted. So as well as keeping your components safe, a good quality PSU may also save you some money in the long run.

My recommendation is to choose a good quality PSU from a trusted manufacturer. Corsair, Cooler Master, bequiet!, Seasonic, Silverstone, EVGA and Thermaltake all usually make good quality power supplies. Use a PSU calculator to work out how much power you are likely to need – including any components you think you are likely to add in the future – and then add about 10%. I suggest you buy at least gold-rated PSUs and get modular or semi-modular if you can.

James