How to Choose a PC Power Supply
NOTE - This page still needs to be expanded and neatened up but does currently have a lot of useful information.
To choose a PC power supply, make sure it has the following:
- More wattage than needed
- Room for growth
- Correct form factor and connectors
- Quality ( important - see below )
Keep reading for more information about how to do this.
TIP - read reviews ( I like Tom’s Hardware )
Newegg has a really helpful power supply calculator that can help you find out how many watts you need: HERE
Why it matters:
- Because you want:
- Reliable power
- Clean power
- To avoid:
- Instability that can be hard to pin down
- Random resets and freezes
- Failing power supply
Things you might want to consider:
- Temperature ratings
- Build quality
- Get a little more than what you need.
- Consider any upgrades or expansions that may require more power.
- More RAM
- Second hard drive
- More powerful GPU
- Cooling system
PSU Brands and Quality
A lower quality PSU can cause problems. You probably want to make sure that you have a good name brand. A name brand does not necessarily mean good quality though. These days I prefer EVGA. You will probably be fine with any of these brands:
- Cooler Master
Power Supply Ratings and Features
Continuous power - “Maximum Power” of a power supply is the continuous (stable) power delivered consistently. Peak power - max power the PSU can deliver, a surge ( like 15 seconds )
Make sure you have enough continuous power.
- Power supplies only use as much power as is needed. Higher rated power supplies just cost more. They don’t burn more power unless needed.
- Overvoltage protection - The power supply will shutdown if the output exceeds a certain voltage limit.
- Overload and overcurrent protection - Excessive load or current will cause the power supply to shutdown which helps to protect the computer and the power supply.
- How much DC power is sent to the computer
- How much energy is lost as heat
300 watt PSU efficiency example:
- 85% efficiency rating - PC pulls approximately 353 watts of input power
- 70% efficiency rating - PC pulls approximately 428 watts of input power
A more efficient power supply will produce less heat resulting in the following:
- quieter system due to fans not working as hard
- longer lifespan
- better reliability
What is 80 PLUS certification?
This is a certification that indicates that a PSU meets specific efficiency requirements. PSUs are rated by independent labs.
|% of Rated Load||10%||20%||50%||100%|
|80 PLUS Bronze||–||82%||85%||82%|
|80 PLUS Silver||–||85%||88%||85%|
|80 PLUS Gold||–||87%||90%||87%|
|80 PLUS Platinum||–||90%||92%||89%|
|80 PLUS Titanium||90%||92%||94%||90%|
- Most important
- Feed power hungry components ( ex. CPU and PCIe GPU )
- 18A needed for current mainstream computer
- over 24A for 1 high end GPU
- at least 34A for an SLI/CrossFire system
- each +12V rail may have different amp output
- amps should be looked at in terms of the combined output of all +12V rails ( can’t always just add them up, check the specs )
- How many +12v rails does a PSU have?
- only 1
- easier because you don’t need to match components to rails
- a failure could affect all components
- multiple rails
- additional protection
- more effort to set up
- only 1
other rails …….
Match your case and system board.
- EPS12V, SFX12V, and Others
AT - legacy
- added to AT
- extra +3.3V rails
- single 20-pin main power connector
- soft-off feature - can be turned off by software
- ATX 2.03 is getting older too
- current, standard choice
- Same shape and size as ATX
- ATX12V v1.0 added to ATX
- 4-pin +12V for CPU
- 6-pin auxiliary connector with +3.3V and +5V
- ATX12V v1.3 added
- 15-pin SATA connector
- ATX12V v2.0
- main power connector changed to 24-pin instead of 20-pin
- removed 6-pin auxiliary power connector
- isolated current limit for the 4-pin CPU power connector for the 12V2 rail
- ATX12V v2.1/v2.2
- requirements for efficiency and other things
- 8-pin CPU connector in addition to 4-pin CPU connector
- Other differences from ATX12V ….
- Entry level servers and high end desktop system boards
SFF - (Small Form Factor) - small power supplies
- Physically smaller than ATX/ATX12V
SFF From Factors
- SFX12V (Small Form Factor)
- CFX12V (Compact Form Factor)
- LFX12V (Low Profile Form Factor)
- TFX12V (Thin Form Factor)
- powers mother board
- 20-pin and 24-pin ( probably has both )
- 24-pin is newer
Processor power connector
- 4-pin and 8-pin
- 8-pin is newer
4-pin Molex connector
- very common
- older hard disks, fans, optical drives, etc.
SATA power connector
- for SATA drives
- Molex to SATA
- cables permanently connected to PSU whether needed or not
- less resistance
- less complex
- cables added as needed
- more organized
- less cluttered
- more resistance
- more complex
- some cables are permanently connected ( ex. main connector )