Other Components

• The central processing unit (CPU) is not the biggest power consumer in many computers: that title belongs to the graphics card. Newer and slower-clocked quad core processors can use 65 watts or fewer, which can bring down the total need for power. However, the other components still use more power than the CPU. You can get away with a 400 watt supply if you have a lower-consuming CPU.
  
  

Consumption Exceptions

• It is possible to get away with a 300 watt power supply if the computer will not be doing graphically intense work. Peak power consumption occurs when the CPU and graphics card are being pushed hard. Conversely, a graphics heavy computer may need more than 600 watts.
  
  

Average TDP

• Computers very rarely -- if ever -- use 100 percent of the power supply's output, its thermal design power (TDP). It is recommended you use a power supply that can support 90 percent of the power needed by all computer parts. Therefore, a 130 watt CPU will use about117 watts under a very high load.