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Beginners Guide to Power Supplies

This guide will give any reader the basic knowledge to comfortably go and purchase a new PSU that is a suitable unit for their PC. Remember more specific advice is available from our sales and technical teams both pre and post sales.

What is a Power Supply and why do I need one?

Power supplies (PSU) are often neglected when building a computer system.  The power supply distributes the power to all the individual components within the PC, without it your PC would not run.

Why is there a price difference between models with the same output?

The quality of components and technologies used to manufacture PSUs varies greatly. A poor quality power supply can greatly reduce the lifespan of your components, cause instability and even fail when overloaded. A high quality PSU will provide a more stable, more reliable system that will also produce less noise and heat. The higher quality power supplies will also operate more efficiently reducing your electricity bill and helping the environment. Remember not all power supplies are made equal.

What do the wattage ratings mean?

The wattage rating on a power supply can be deceptive as it shows the combined wattage across all the rails (basically all the connectors on the PSU are added up for the total power output). With the increased demands by components, the total required output for the +12V line has become increasingly important. A power supply should ideally have at least 18A available on the +12V line. The actual load you will need to get the most out of your components will vary depending on your system specifications.

What do power supply efficiency ratings and certifications mean?

If a supply loses less than 20% of the total power consumed, then it is considered ‘efficient’.  Look for the ‘80Plus’ sticker on modern PSUs. The benefits of more efficient power supplies are lower electricity bills, less harm to the environment and also due to less energy being wasted as heat a cooler and quieter operating PC. There are four 80Plus levels:-

- 80 PLUS Bronze: 81%+ efficient
- 80 PLUS Silver: 85%+ efficient
- 80 PLUS Gold: 88%+ efficient
- 80 PLUS Platinum: 90%+ efficient

What most people do not realise is the added benefit to a higher efficiency power supply is lower heat output. With less heat the fan on the PSU can keep temperature down  allowing for a cooler and quieter system overall.