Too Much Power Supply?

When building or buying a Custom PC, the power supply is a critical component that needs proper consideration, Too often people purchase a PC or build a PC with the thought of "I want to get the biggest power supply that I can buy..."  but that's a big component that can be over bought and money that could be put towards other components ends up generating power that never gets utilized.

What does the wattage actually mean on a Power Supply unit?  The wattage is the amount of power made available to the system.  However, there is an extra factor you must take into account, and that's the fact that what the power supply does is convert from AC to DC.  When this happens you have a loss of energy in the way of heat, and the process itself.  Most power supplies are at least 80%+ efficient (Bronze, Silver, Gold, Platinum are just how much more than 80% it will be).  That means for a power supply that generates 500 watts for the system it powers it actually is using roughly 625 watts from the wall.  So keep that in mind when you are pricing the power supply.

What does the form factor mean when it comes to power supplies.  Simply put the form factor for the power supply must be compatible with not only the system case that you are putting all your components in, but the system board must also be compatible.  So if your Case is AT/ATX/MicroATX compatible, your power supply must match to fit the case, and match the system board so that the cable harness would have the appropriate connections.  That is important to remember as well.

So we now are sure that the system board, the system case, and the power supply will fit.  Now how do I know which wattage is right for the system being built.  Let's now look at how to calculate system needs.  It all boils down to a fully thinking out your system, what components you need.  Let's look at a bare bones PC next to a more advanced system.

Basic System

Componenet	Description	Wattage
CPU	Basic Dual Core	65
System Board	Basic Board	40
Video Card	Basic Add-on Card	35
Memory	Basic 4GB	5
Optical Drive	DVD-ROM	6
Hard Drive	5400RPM HDD	10
Fans	Basic Case Fan	4
	Total	165 Watts

Advanced System

Componenet	Description	Wattage
CPU	Advanced Hexcore	150
System Board	Advanced Feature Set	55
Video Card	Advanced Graphics (Dual Card)	350
Memory	Advanced 8GB	10
Optical Drive	Blu-Ray	12
Hard Drive	7400RPM HDD (Raid 1)	20
Fans	Basic Case Fan	4
	Total	600 Watts

So as you can see the more complicated the system the more power you need to make sure everything functions correctly.  So the basic setup will do fine with a 200 watt power supply, and the advance will need a 650-700 watt power supply.  These numbers are based at max power draw per component.  That is what you need to calculate at.  The most common mistake you find is people calculate on the idle voltage draw, As soon as your system is taxed, you will suffer from power issues.  If you plan to increase storage, plan accordingly for your end product not with what you currently have.
Now that you have an understanding of how to better choose the proper power supply, I hope this will help you with your next build, and also to not get sold something that is not what you need.