Guidelines for Selecting PC Power Supply

For those of us who build our own PCs, selecting the power supply is an important decision, and its easy to over-estimate one’s needs. Below are some guidelines:

First of all, the power supply only draws the amount of power that the computer is consuming (minus the heat, maybe 20% in an 80% efficient power supply). There has been some confusion in online blogs where folks thought that a higher capacity power supply (in watts) would consume more electricity–not true.

I have read some articles from people that looked deeply into the underlying technologies that suggest the power supply be over-rated by maybe 50% over what it will actually be asked to provide. I believe the CPU and video card are the only big watt consumers in my systems.

I have also read, again from people getting down to the circuit topologies and part quality of power supplies, that there are a wide variety of quality levels available for a power supply of a given capacity, so it is worthwhile to buy reliability and stability by spending more than the minimum for a given watt level. What this has lead to me personally seems pretty mainstream in terms of the product space. I have three computers set up with corsair 500 watt 80+ efficiency ‘bronze’ rated power supplies–$62 American. I note at micro center, 400 watts is the smallest one they stock so its on the low end size-wise. In future builds I will likely spend more per watt to get even more quality–though I have not had any problems with this model and brand.

For my system, this is what I estimate for max power needs: xeon 1276 85 watts. GTX 1050 video card–75 watts max during gaming. I note the pci-e spec is 75 watts max delivered thru the pci-e slot. If a video card can draw more than that, then it has one or more sockets on it for power supply cables. Best I can tell, an SSD can draw maybe 2 watts and a hard disk 10. I have an SSD and an m2 and a spinning platter, so that would be 14 watts. So, this totals 174 watts. Add a few watts for mobo, ram, and usb devices very conservatively gives a max consumption of 200 watts. Less than half of a 500 watt power supply. I note the i7-8700k, considered to be a popular high end CPU for audio, is rated at 95 watts at standard clock speed.

So for audio recording and production, I imagine it would be an unusual system that really needs a 750 or 1500 watt power supply my recommendation is to spend more money on quality than excess power capacity. For overclocking, I don’t have the knowledge to speak to this–adding water pumps, tons of fans, and whatever more power the CPU draws when the clock speed is increased–lots of OC information on the interweb for that.

In any case (bad pun?), anyone assembling a system can run their own numbers and not simply guess on power supply sizing. If I have the numbers wrong, or am missing something, glad to be educated.

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