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PC Power Supply Unit ..the cost of running?

Discussion in 'General Hardware' started by reepo, 30 Jul 2006.

  1. reepo


    Joined: 19 Jul 2006

    Posts: 1


    since my PC is always turned on, i have become quite conscious of my electricity bill and trying to keep costs down, especially with the ever increasing rise in bills in the UK (eg. i have gone for a TFT monitor now as they are cheaper to run than a CRT..)

    anyway, my question is to do with PSU's. If i use a 300w power supply unit as opposed to a 600w one (and let's say my computer is just idle doing nothing but switched on), from a money point of view, is it actually costing me more in electricity to run the 600w power supply. or does it make no difference which PSU i use but instead it's all to do with how much power the PC components/drives are drawing from the PSU?

    in fact on the subject.. if a PSU is rated at let's say 300w, and let's say a normal household lightbulb is 60w.. in money terms is my PC using as much power as 5 lightbulbs then?

  2. ukdave


    Joined: 4 Oct 2003

    Posts: 280

    Location: UK

    As far as I know a 600W PSU providing 300W of power uses the same electricity as say a 400W PSU providing 300W. However it will depend on how efficient the PSU is.

    For example, some nasty Q-Tec PSU would use more power because its efficiency is low (hence their horrific heat and noise output). So a PSU efficiency value is something worth checking out, i believe Tagan/OCZ are good in this area.
  3. Corasik


    Joined: 5 Jan 2003

    Posts: 5,002

    Location: West Midlands

    In general it's the efficiency of the PSU not the total wattage that matters.

    However in the extreme's things can be a bit 'different' If you had an ultra low power system, that draw say 50 watts idle, and tried to power it from a 1000 watt PSU, the chances are at such a lower power level, the 1000w PSU would be pretty inefficient. However by the time you got up to 200w, then the 1000w supply would probably be back into its efficiency band.

    Likewise a 400W PSU loaded over 350w for example 'might' start falling out of its efficiency band.

    PSU's from Seasonic are very unusual as they are generally better than 80% power efficient from 10%-90% load.
  4. manveruppd

    Wise Guy

    Joined: 24 Feb 2004

    Posts: 1,086

    Location: Leeds/Cyprus

    Yep, check out a few reviews and look at respective efficiency ratings (any half-decent online review site will test for efficiency in their benchmarks). Generally, a PSU which advertises "Active PFC" (which is offered by all good brands) will be much cheaper to run than a no-brand generic PSU.