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The PC Power Supply Guide for the Masses

  1. Introduction
  2. PSU Abbreviations and Glossary
  3. Connectors used in a PC Power Supply
  4. PSU cables: Non-Modular, Modular and the middle-ground!
  5. Power Supply Labels
  6. Power Supply Form-Factor- ATX12V
  7. Power Supply Form-Factor- SFX12V
  8. Basic requirements of a power supply
  9. Facts about 80 Plus Certification
  10. Protection Circuits and Features
  11. List of Power Supplies, OEM and Review Links
  12. Common PC Power Supply Myths
  13. Resource Links and References
  14. View All


Ampere is a term used to measure electricity. In relation to power supplies, it points out the amount of electric current pushed through the voltage rails on the power supply.


Capacitors are components used to store power, in many electrical and electronic devices. In relation to power supplies, good quality power supplies are able to function provided they are made of good quality. These capacitors are made by several electric component makers, and these capacitors usually have a power and temperature rating.


In relation to PC power supplies, there are two circuits- Primary and Secondary

  • Primary circuit takes power from the socket wall (AC power) and through sub-components within the power supply. This includes components that filters and converts AC to DC power.
  • Secondary circuit is where the power supply uses the DC power and provides power to PC components via rails.


Lik all components, power supplies need cooling. Like many components- there are two cooling: active and passive. Active uses fans to either push or pull air for the power supply. Passive are usually larger array of sinks to keep the components cool. Unlike active cooling, passive cooled power supplies need a lot more planning to help dissipate properly. Usually, passively cooled power supplies are made for quiet-themed PCs, though manufacturers started using better bearings or fans from better manufacturers and even implemented PWM or thermally controlled solutions.


In relation to PC power supplies, efficiency indicates the usable DC power after converting from AC to DC. During conversion, some amount of power is lost in the form of heat. Having good components and sub-components with higher rating under higher temperature condition usually translates to higher efficiency. Efficiency is rated using % value. Efficiency of a power supply is tested under two types of load using a fixed temperature.

There are two types of load pointed out by manufacturers- Continuous and Peak.

Continuous indicates that the power supply is rated to run maximum amount of power a unit can for a very long time (typically, hours). Peak is a rating that indicates peak power output for a very short amount of time- usually minutes. No good power supply manufacturer will use peak ratings.

Ideally, all power supply manufacturers should advertise Continuous. The ones that advertise peak load should always be avoided at all costs since it provides a certain amount of power for a very brief moment, usually a practically that lower quality power supply uses.

Some manufacturers post both Continuous and Peak. While this isn’t harmful, only continuous power should be given importance to.

Efficiency of load is tested in certain temperature workloads. Since PC is a closed case setup and AC to DC leads to a certain amount of heat, it needs to be tested at a higher temperature condition. Some manufacturers test it at room temperatures to point out high-efficiency value when advertising (some are known not to point out typical temperature). These should be avoided as typically an internal temperature could go up to 40 degrees Celsius depending the ambient temperature. 40 degrees Celsius is the commonly used condition. Some manufacturers are known to use 50 degrees Celsius. In most cases, some claim that this is unrealistic temperature conditions, but manufacturers do this to point out high-quality components, its lifespan/(MTBF) and higher efficiency rating even in seemingly unrealistic temperature conditions. It should also be pointed out that in a closed case PC setup, eventually the system will accumulate dust. Dust is one of the air flow obstacles and when it does block air flow in a power supply, the temperatures would naturally increase. Testing the power supplies in 50 degrees Celcius in my opinion helps to stimulate that condition.

Note that in typical power supplies (even the high efficient variants) have lesser efficiency at lower loads compared to higher loads. This is the reason why proper power supply reviewers test a power supply with variable load- 20%, 60%, 80% and/or 100. The variable load varies from reviewers but typically they point out efficiency in lower power consumption, typical load power consumption efficiency and maximum efficiency it can produce.

Therefore, buying a high-wattage (even the high efficient) power supply for a system that consumes lesser power even at maximum load is counter-productive. One of the typical ways to find the right wattage is by use certain wattage calculate like how Coolermaster has. This helps you to get a rough idea of the wattage unit you should be looking at. Note that CM’s power supply calculator points out wattage, and not amperage. While it does give a ballpark figure, it’s best to check reputed review websites that have proper equipments.

It should also be noted that the quality of the power output degrades in time. Therefore, one of another advantage of using power supplies with better components also ensures long life span of the unit.


In general term, heatsinks helps to remove heat from a particular components by the means of close contact and helps them to dissipate heat by drawing the heat away from the component. It is either dissipated passively or via active methods using air. Commonly, they’re made of aluminum but really good power supplies made specifically for extreme loads use copper.


Abbreviation for Mean Time Between Failures. It’s a unit of measure to indicate the reliability of any hardware component. In relation to power supplies, different manufacturers rate MTBF differently, depending on the series sold for a specific type of uses (general, lower power, gaming, high-end PCs). Like efficiency, Some manufacturers measure MTBF at room temperature, which is wrong considering a close case setup will typically be much higher time a normal room temperature. If an MTBF of a power supply is determined using ‘room temperature’, that means in actual temperature conditions (typically 40 degrees Celsius is considered as ideal operational temperature), the MTBF is significantly lesser as heat will eventually degrade the components on the power supply.


OEM is an abbreviation for Original Equipment Manufacturer. In relation to power supplies, most of the brands get their power supplies made by certain manufacturers. This carries weight when choosing power supplies because depending on the OEM, they do not compromise quality depending on the usage and purpose (general, server, enthusiast grade). Some of the OEMs sell their power supplies in that are available in retail while other OEMs are build-to-order. In many cases, brands are known to re-label the specific OEM units, with minor differences such as casing/ fan colour, brand labels, cable sleeves, etc. Some recommend tweak for additional efficiency, just as increasing the amperage capacity of certain capacitors or adding additional filters and protection circuits.

Not all are OEM though some well-known brands choose well-known OEMs and prefer not to involve themselves in the technical aspects, at least in the start. Some do design their own power supplies, or make certain tweaks on existing OEM models, but they do not have their own manufacturing division for power supplies. The latter is usually the case, whereas some brands prefer the former, but that’s also what sub-standard PSU brands do.


There are two types of PFC- passive and active. Most power supplies that you get now are active, but both should be differentiated for better understanding. In a very basic sense, Power Factor Correction helps to draw AC power from your mains as smooth as possible to ensure smooth operation. This ensures that the power supply draws power from the AC line properly.

Passive PFC is a much cheaper solution but doesn’t really provide a strong PFC protection that a power supply should. In many countries, any power supplies and power bricks with passive PFC function is avoided from being imported. Active PFC is the best implementation for power factor correction and also adds up cost to your existing units. A lot of power supply manufacturers in this day of age prefers to use this for having their product available worldwide.


Stands for Power Supply Unit. The unit is a component that converts AC to DC for computers. It also helps to condition the power meeting certain standards of quality and safety which varies between companies and their series.


In relation to PC power supplies, it means power via different channel produced by the PSU after converting AC to DC power. Modern power supplies need to comply with ATX PSU standards set by Intel. Different channels found in power supplies are +12V, -12v, 5V, 3.3V. It should be noted that some power supplies provide multiple +12v rails. However, its only the ones that have independent channel from the power supply are true multiple +12v rails. Others are usually used as marketing tactic, but in reality they split from the same +12v rail.


In relation to PC power supplies, ripples are usually identified by power supply reviewers with a proper set of equipment with specific functions. Generally, the more ripples a power supply creates while delivering DC power to the PC components, the higher the potential to reduce the lifespan of the capacitors and components. Sub-standard power supplies tend to have much higher ripples which eventually creates instability and even irreversibly damage components.


  1. Koolest ripper guide to What is and what is not on SMPS!
    Thanks for adding those SMPS suggestions! 🙂

  2. Much appreciated!

    I plan on putting more guides per component so that many people from newbies to regular users can understand “what is” and “what is not” for many components to help them make better purchase decisions! This way, we can guide even the newest of end users to understand whenever they read our reviews!

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