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A cheap power supply isn't a good place to try to save money, although it's often the first place less experienced builders will try to go cheap. As a general rule, you want a well-built power supply that conforms to modern technical standards, and you can expect to spend at least $40 on it. Decent PSUs priced under $30 simply do not exist. Keep your eye out for the following safety-oriented features:
|SCP||Short Circuit Protection||Required|
|NLO||No Load Operation||Optional|
The capacity of your power supply really depends on the components going into your PC. Our basic build, without discrete graphics, would easily be fine with a 250 W PSU. If we add a budget-friendly graphics card priced under $100, 300 to 350 W are plenty. However, if you jump on Ebay and grab a former flagship priced inexpensively, you'll probably want something able to sustain 350 or 400 W.
Now, those numbers represent current from the 12 V rail. To be safe, we recommend a 450 to 500 W power supply. And stay away from cheap PSUs that emphasize less-taxed 3.3 and 5 V rails.
Let’s have a look at our two builds and their power requirements. In the chart above, we have the build designed for basic productivity, without discrete graphics. The chart below represents the more advanced configuration, sporting an add-in graphics card.
Manufacturers have managed to reduce the power draw of their components at idle over the years. So, the difference between idle and load power is greater now than ever before. Since a PSU’s efficiency drops off dramatically below roughly 20 percent of its maximum current, it makes no sense to use a power supply able to supply more wattage than a system will ever need. You'd only want to buy a higher-capacity PSU if you're using (or planning to use) a higher-end graphics card, for example.
|Without Discrete Graphics||With Discrete Graphics Up To 100 W TDP||With Discrete Graphics Up To 200 W TDP|
|PSU Recommendation||300 W (80+)||350 W (80+)||450-500 W (80+)|
You can get a decent, reliable power supply for about $40. It’s important to check that it has all of the safety features we mentioned above and, in case you want to use an older graphics card, all the necessary connectors (like auxilary PCIe power cables). Also, it’s always a good idea to read power supply reviews first; that could save you a lot of trouble down the road.
Now, we need an enclosure in which to put our hardware. So, cases come next.