How in the Tech

Determining Necessary Power Supply Wattage

By Adam Myers ⋅ July 13, 2009 ⋅ Tags: System Administration

Computer enthusiasts who build their own computers component by component or otherwise in the continual upgrade phase need to be aware of the power requirements of their fresh silicon. The fact that power supplies available today range from a paltry 300W to a jaw-dropping 1000W+ tells you there is a lot of variance on requirements. Logically, a quad core CPU is going to take more than a dual core or 3 hard drives require more juice than 1. How much is enough though and how much overhead should you account for in order to future proof your initial purchase?

Newegg, likely the number one PC components site for enthusiasts, has a Power Supply Calculator form that aims to alleviate some of the guess work during the purchase process. Many how-to sites recommend purchasing a high-end and high wattage power supply to remain on the safe side but that actually isn’t the best advice, it’s just the easiest answer. The truth is, you probably don’t need to pay the premium for wattage you will never use.

The calculator provides drop-downs to aid in spec’ing out your potential purchase and offers a recommendation for the total wattage necessary. Requirements change depending on the processor, video card, or number of hard drives or memory sticks. My build suggests a 461W PSU and to give me a bit of future proofing on my purchase, a 550W sounds about right.

Newegg’s form should give you a great starting point to work from but as components are ever changing – it will always lag behind the very top of the line video cards and processors. Just keep that in mind as you work on assembling the latest and greatest.