PSU Wattage Rating & UPS

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ImHappy_FeelinGlad

ImHappy_FeelinGlad

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My main question is: is the wattage rating on a computer's PSU in terms of 12 volts (the voltage used within most of the computer) or 120 volts?
My reason for asking is that I am looking to buy a UPS for my computer, and I want it to handle my computer at maximum power usage (although that will likely never be necessary). My computer has a 550W PSU, and the UPSes I've seen in stores are very expensive at that wattage rating.
Considering wattage = voltage x amperage, it obviously makes a considerable difference in the UPS I need to buy.
Thank you all very much in advance, happy building!
 
Solution
Rogue Leader


No, your computer can draw up to 550 watts from the UPS, well in theory if you maxed out your components. the reality is your components probably will only draw about 350 or so watts depending on your system specs (I can tell you if you post them). Your monitor draws very little...
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Rogue Leader

Rogue Leader

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A PSU's wattage is based on 12 volts.

Now as for buying a UPS, the optimal UPS to buy would be one that matches your PSU's wattage, this would cover you in every way. BUT Its understandable that that may not be possible. As long as you get a UPS that will match your system's maximum power DRAW you would be ok.

For example I have a 750w psu, but my UPS only allows 600w. Being that my system only draws about 420w tops I'm fine. Just because a PSU is rated for say 600w, it doesn't mean it will draw that at any point, unless you've attached such hardware that needs it.
 
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mjslakeridge

mjslakeridge

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And, keep in mind that the average consumer UPS is not designed to be able to run the computer and monitor, etc. for a long time when the power goes out. Just for a few minutes to allow you to safely shut down the system. I have seen charts that show how many minutes various UPS allow at 50% load, 100% load, etc. If you have a specific UPS in mind, their website should have this information.
 
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Rogue Leader

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Right, most last maybe 15-20 minutes tops. Luckily monitors use very little power.

Unfortunately however you are limited to the maximum wattage of the unit even when running off wall power and not the battery. This is due to the circuitry of the UPS device. Something to keep in mind and why I wrote what I did above.
 
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ImHappy_FeelinGlad

ImHappy_FeelinGlad

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In other words, in relation to my UPS, my computer would be drawing a maximum of 55 watts (at 120V)?
Right now, I am just trying to make sure I get a UPS that can handle the wattage of my PC and monitor at one time (like you have to do when picking a PSU). I am aware that a cheaper UPS would not allow a long amount of time off of mains power, but enough time to shut down safely is all that's really necessary.
 
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Rogue Leader

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No, your computer can draw up to 550 watts from the UPS, well in theory if you maxed out your components. the reality is your components probably will only draw about 350 or so watts depending on your system specs (I can tell you if you post them). Your monitor draws very little wattage.

In other terms your 550w PSU usually draws around 4-5 amps from the wall, to make it easy 4 amps x 120v = 480w power draw. Inside the PSU that power is converted to 12v and output to for example 48 amps on the 12v rail, 20 amps on the 3.3v rail, 20 amps on the 5v rail. Different math but added up comes out around 550w.
 
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Solution
ImHappy_FeelinGlad

ImHappy_FeelinGlad

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Jan 10, 2017
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Now I get it... thank you very much. So I should really plan accordingly for something close to my PSU wattage rating in regards to the maximum power draw at one time. Thank you!
 
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