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FX PC Buying Guide - Power Supply

August 13, 2019 5 min read

Power supply is the “Power Plant” of your system. It supplies the required amperes and voltages to each component that is connected to function properly. But not all power supplies are created equal. There are the high quality “branded” and true rated power supplies, and the so called “generic” power supplies. Branded power supplies are made by known brands and has efficiency and safety features built in it, while the generic ones doesn’t have these features plus the built quality is subpar compared to branded units. Pairing you high-end system with a cheap power supply will mess things up - unstable and intermittent power during operations, or worst, the power supply blow up and take down some components if not all. Pairing your low budget system with a premium power supply is overkill and waste of money. So you have to pay attention to what kind of system you will build or already have to appropriately select the power supply you will buy. And here are our list to consider to help you pick the power supply.


Each components in your system - the processor, motherboard, graphics card, hard drives, fans, and others - consume electrical power measured in Watts. The combined wattage of each component is the wattage the power supply should be able deliver. There are PSU Calculators out that can compute the power consumption of your system and recommend how many watts the power supply should have. The Load Wattage of our example system is 415 watts and the recommended PSU wattage id 46 watts. It means that the power supply you should buy can deliver 465 watts. Though a 450W power supply is enough to power this system, the site recommends, and we do also, to have at least 50 watts of headroom from the actual load wattage of the system. Since there are no 465W power supplies in the market, we recommend getting a 500W power supply for this particular system. Also pay attention to the “continuous” or “total”output power, Pcont in our example power supply. It is the power it can deliver continuously, not the “peak”. Peak output power is the highest wattage the power supply can deliver in a given moment. Mostly generic power supplies put this as the actual wattage of the power supply, which is not.


Protection Circuits are are additional components used to monitor current, voltage, temperature, and others to ensure that the monitored values are within the threshold. Basically they trigger safety operations to prevent further damages like shutting down if the monitored values exceeded the limit. Common protection circuits are
  • Over / Under Voltage Protection OVP UVP
  • Short Circuit Protection SCP
  • Over Temperature Protection OTP
  • iom Over Power / Load Protection OPP OLP
  • Over Current Protection OCP
Some branded power supplies only has a few of these protections, premium power supplies may have all of these, and generic power supplies may not have any of these at all. Look around the box of the power supply to see if it has these protections. If don’t see it, look at the manufacturer’s website to confirm its protection features. You can read this article for in-depth explanations of protection circuits in power supplies.

Efficiency Rating

Efficiency Rating is how efficient the power supply in power consumption. A 500 watt power supply supply is not exactly consuming or pulling 500 watts from the wall electrical socket. It is always higher than its rated power. If the 500 watt rated power supply is pulling 650 watts from the wall, then it is 77% efficient. An independent certifier tests the power supply units from the manufacturer and award the 80 Plus (80% and above) certification if the unit passed. Why you should bother about this 80+ certification? Two things - electricity bill and temperature. First, the 77% efficient 500 watt unit will consume 650 watts while the 80% efficient unit will only consume 625 watts. You power consumption will be 25 watts less, sum it up for a month, depending on your kW/H rate, that will be your saving. Secondly, the 125 watts - from an 80% 500 watt unit - is converted into heat. So the 77% power efficient power supply will run hotter because it needs additional 150 watts to supply 500 watts of power, while the 80% power efficient only needs additional 125 watts. Heat is one the deteriorating factor in most of electronics equipment, this is why most of the 80+ certified power supply last longer than non-80+ certification. An 80+ certified power supply unit has 80+ certification logo in its box or in the unit itself. You can read more detail on 80 Plus Certification here.

Connectors and Cables

Check your components and motherboard and buy the power supply that has the right connectors for the components you have. Some motherboards require 8-pin EPS12V connector, but not all power supply has that type of connector especially the cheaper units. Your video card may need and 8-pin + 6-pin PCI-E connectors, or your selected power supply has 7 SATA connectors which maybe too much. Some manufacturers give the length of the cables and the layout of the connectors that can help you managing the cables. Modular power supplies are becoming more popular and you may want to consider this feature. Modular power supplies has detachable cables and allows you to connect only the ones you needed and leave the unneeded cables unattached. This is very helpful in managing the cables and make yours build looks neat. Semi-modular power supplies has the main power connectors attached to the main unit while the peripheral connectors are detachable. These types of power supplies are usually more expensive than non-modular power supplies.


Your power supply should be compatible to your computer case. If you have an ATX case, your power supply should be ATX compatible, which most of the power supplies were made. If you have an ITX or a slim case, check carefully its power supply compatibility. Usually they require an SFX power supply. If you bought a slim pre-built system and you need to replace its power supply, it is recommended to buy the same-sized unit that will fit into the case.

Features You Can Ignore

As manufacturers are getting more creative in putting new innovations and technologies, its quite unavoidable that some of these are useless to majority and would costs only additional bucks. These are, based on our opinions, the features you can ignore.
  • Zero RPM Fan Mode - This feature turns off the fan completely until it hits certain temperature.
  • Fanless - These models have no fan at all. The heat is mixed up into the computer case.
  • Water Cooling - These units has water block in it and there are only very few of these.
  • RGB - Unless the manufacturers allows you to use this feature for temperature monitoring, where you can set a specific color for a range of temperature, then this feature is only for aesthetics.
  • Flat cables - Flat cables are easier to bend and route making it easier to manage the cables. With a little more patience, you can still manage the cable routing as good as the flat cables with normal cables.
We are not saying that you should avoid the unit or the brand, if additional buck won’t hurt you or it fills your specific needs, then you should consider these features.

Reviews and the PSU Tier List

Lastly, read user and expert reviews of your selected power supply before buying it. Tech and computer sites do test and even stress the unit and give expert recommendations and alternatives, while user reviews share their experiences with the product which can be very helpful in deciding which power supply would you buy. As for the PSU tier list, we don’t exactly recommend it and be your ultimate basis in buying a power supply. Those are our guidelines which hopefully will help you decide the best power supply for your system.

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