1. This forum is in read-only mode.

Confused About the Results of Computer Power Usage Calculation

Discussion in 'Computers & Modding' started by Cahos Rahne Veloza, Jul 2, 2016.

  1. Cahos Rahne Veloza

    Cahos Rahne Veloza The Fart Awakens

    I used this free service to guess~timate the total combined power usage of my system:

    http://outervision.com/power-supply-calculator

    And according to its calculations my system eats up 287 watts per eight hours of use per day of usage. It also stated I need a PSU that can handle 337 watts, as if there are PSUs with exactly that amount of power :-/

    Anyway, regarding PSUs I've decided to go for a 620 watt PSU as loony and I talked about on this thread:

    https://forum.romulation.net/threads/which-psu-is-better.64702/

    But I got confused by the calculation's suggestion regarding a UPS, as it said I'd need a 600VA UPS, nothing out of the ordinary there, you might say.

    My confusion comes from the fact that the calculation said I'd need a PSU that can easily handle 337 watts of power, however most of the 600VA UPSes (actually the most common ones I've seen are between the 625 to 650VA range) I've seen only have 325 watts of output capacity. I'm a bit worried that that twelve (12) watt difference might make the UPS a bit under powered to handle my system. So does those two wattage values need to be equal or will it be just fine? I'm guessing I'd need the UPS's wattage to be equal or higher as an optimum, am I right?

    I could just over shoot and get something like a 900 and up VA UPS but those things are extremely expensive and way out of my budget.
     
  2. Loonylion

    Loonylion Administrator Staff Member

    unfortunately its a common misconception that watts and volt-amps are the same; they aren't..

    PSU calculator will be for the draw at any given time (either the peak draw or the continuous draw). From what you've written, 287W is the continuous draw, and 337W is peak (i.e when its just turned on, or its being fully loaded)

    The APC UPS selector suggests a 750VA UPS based on a 400W continuous load and 20 minutes run time, the UPS would be running at 67% capacity.
     
  3. Cahos Rahne Veloza

    Cahos Rahne Veloza The Fart Awakens

    Oh so the 287 watt value is just for idle consumption and the 337 watt value is for when the system is in peak usage?

    I see, so my current 620 watt PSU is definitely enough to power my system.

    Now regarding my other concern, so I should get a UPS which is 700VA or higher then?

    By the way, you haven't answered my other query regarding the significance (or lack of) of a UPS's wattage value. As an example, this 625VA APC UPS:

    http://www.lazada.com.ph/apc-atago-bx625ci-ms-625va-ups-305606.html

    Is rated at 625VA with 325W configurable power. So does this mean the unit can only handle a computer whose peak power draw is 325watts or lower?

    As for the two variables you mentioned, 400 watts continuous load and 20 minutes of run time, I'm probably not going to reach 400 watts of usage since as the calculations pointed out my peak consumption is at 337 watts and I don't think I'm pulling that much for eight hours straight, maybe two to three hours at max. Quite frankly I don't even keep my system turned on for more than four hours straight these days anyway.

    As for the twenty minute UPS runtime variable, yeah 20 minutes is just enough time to close programs I'd be using and shut the system down during a power outage. Sadly I haven't seen any 700VA nor 750VA UPSes hereabouts lately. Well there are ones from FSP available here but we don't have local FSP UPS Service centers in the country. My only options are UPSes from APC and the last 800VA APC UPS I've seen here ran out of stock three months ago.
     
  4. Loonylion

    Loonylion Administrator Staff Member

  5. Cahos Rahne Veloza

    Cahos Rahne Veloza The Fart Awakens

    Thanks for the help loony as always.