1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Power Consumption

Discussion in 'General Discussion' started by smoove, 24 Jul 2006.

  1. smoove

    Perma Banned

    Joined: 15 Dec 2002

    Posts: 5,392

    How would i workout how much money my pc is costing us on our electricity bill per week?

    Say it draws on 200w for 8 hours a day, for a week? How would I figure out how much im charged per 1 unit of electricity?

    Thanks.
     
  2. Jonny69

    Man of Honour

    Joined: 3 May 2004

    Posts: 17,670

    Location: Kapitalist Republik of Surrey

    You'll be charged about 9p per unit which is 1KW/hr

    so you're drawing 1/5KW x 8hrs x 7days x £0.09 = approx £1 per week

    Not exactly that simple because usually the first X number of units is charged higher so it's probably closer to £1.25
     
  3. fatmas

    PermaBanned

    Joined: 23 May 2006

    Posts: 409

    Location: Swindon

    *Does calculations...*
    No Idea.
    Sorry.
     
  4. Scott Salisbury

    Wise Guy

    Joined: 26 Jan 2005

    Posts: 1,588

    Location: Newcastle, UK

    If I have a 480w power supply, when the PC is switched on, is it constantly using 480w's ? Or does the power it uses vary on what components I have etc?
     
  5. smoove

    Perma Banned

    Joined: 15 Dec 2002

    Posts: 5,392


    Is that all? I would have thought it would have been in the region of £5 per week.
     
  6. Ricochet J

    Capodecina

    Joined: 29 Jun 2004

    Posts: 12,906

    Q = IV
    V = IR
    R = (ρl)/a
    therefore
    Q = (I²ρl)/a (thats (current squared * resistivity * length) all divided by cross sectional area) (where Q equals 1 unit of charge)

    :)
     
  7. fatmas

    PermaBanned

    Joined: 23 May 2006

    Posts: 409

    Location: Swindon

    Your not always using 480w's of power. It really does depend on the PC.
    Well I think it does anyway :-S
     
  8. Jonny69

    Man of Honour

    Joined: 3 May 2004

    Posts: 17,670

    Location: Kapitalist Republik of Surrey

    Yeah it depends on the PC. My laptop draws a lot less than a hulking Athlon dual core with two SLI graphics cards, a pair of Raptors and neons.
     
  9. fatmas

    PermaBanned

    Joined: 23 May 2006

    Posts: 409

    Location: Swindon

    Yeah that makes sense. Have fun running a PC off a battery.
    Even a lot of UPS's only last about 20-40 minutes...
     
  10. Jonny69

    Man of Honour

    Joined: 3 May 2004

    Posts: 17,670

    Location: Kapitalist Republik of Surrey

    And don't forget it'll add about £3 to the bill each year by just being left plugged in and not switched on. The PSU draws about 5W when in standby. This is also the case for your phone charger, the little lights on the front of the video, DVD player, stereo, digibox, monitor, microwave oven etc etc. you can save over £50 a year by just unplugging stuff overnight.
     
  11. Pho

    Sgarrista

    Joined: 18 Oct 2002

    Posts: 9,190

    Location: Derbyshire

    Best bet would be to buy one of these 'Energy Cost Meter' things for £20 or so (theirs some cheaper £10 ones too)

    [​IMG]
     
  12. pinkacidbootson

    Mobster

    Joined: 9 Mar 2006

    Posts: 4,001

    Location: Rhone-Alpes, France

    This website allows you to calculate how much power your PC uses (peak usage). Even if your power supply is 600W, it won't use 600W all the time, if at all.
     
  13. cobxx

    Gangster

    Joined: 22 Jun 2006

    Posts: 276

    Worked it out a while ago, it's really not as much as you would think. Sure people with pelts are slightly more conscious of price though :rolleyes:
     
  14. cyborg

    Wise Guy

    Joined: 25 May 2004

    Posts: 1,423

    Location: Belfast

    I was always interested in how much power my pc draws by being on at the wall but shutdown.

    With powersupplys the wattage (which is voltage times the ampage) that is drawn is only what the device is drawing. This is why as long as you use the same voltage you can use a much larger powersupply to power something without blowing it to crap. (6A PSU for something that only needs 3A)
     
  15. clv101

    Capodecina

    Joined: 18 Oct 2002

    Posts: 10,739

    Location: Bristol

    I have one of those and this is what I measured with it: http://uk.theoildrum.com/story/2006/7/1/1033/23099

    Regarding the PC:
    System unit = 180-270 (idle-load). Call it 200W
    Monitor = 85-95. Call it 90W

    But also note the standby consumption:
    System unit = 22W
    Monitor = 27W

    So, 8 hours on would be:
    System unit = 8 x 200W = 1.6kWh
    Monitor = 8 x 90W = 0.72kWh
    Total = 2.32kWh, at 9 pence /kWh that's 20.9 pence per day.

    Should also look at the 16 hours standby (off but not off at the wall).
    System unit = 16 x 22W = 0.352kWh
    Monitor = 16 x 27W = 0.432kWh
    Total = 0.784kWh, at 9 pence /kWh that's 7.1 pence per day.

    So in total that's 28 pence per day or £70 over 250 working days a year.

    The system unit is an Intel Pentium 4 2.8C running at 3GHz with an ATI 9800PRO graphics card and four hard drives. The monitor is a 21" Sony Trinitron.

    For my next system I'm looking at a Core 2 duo due to lower power consumption for the performance and the 7600GT which seems to hardly need any juice at all!
     
  16. Jonny69

    Man of Honour

    Joined: 3 May 2004

    Posts: 17,670

    Location: Kapitalist Republik of Surrey

    That's really interesting to read clv, I was being conservative with a 5W figure for standby but it looks like it's a lot more than I thought. No wonder the bill was so high last time! I'm quite tempted to buy one of those power meters.
     
  17. zetec452

    Sgarrista

    Joined: 15 Sep 2003

    Posts: 9,454

    Those power meters do indeed look good.

    Its interesting how much more power a pc running seti would cost.
     
  18. PeterNem

    Sgarrista

    Joined: 15 Feb 2003

    Posts: 8,322

    Location: NJ/NY, USA


    The power supply won't be 100% efficient... let's assume it's only 75% efficient.

    Therefore to output 480watts it will need to use ((480/3)*4)watts = 640 watts

    HOWEVER... it will only draw as much power as it needs.

    If you're sat idling in windows, your CPU won't be working too hard and neither will your graphics card (two of the biggest users of power). Also your drives will most likely have spun down.

    It'll only go near maximum useage when you're doing something really intensive like gaming. Even then though it'll only use what it needs, which could be 400 watts, it coud be 480 - it depends what you have in your system.
     
  19. smoove

    Perma Banned

    Joined: 15 Dec 2002

    Posts: 5,392

    Another person in the hardware place just said this:
    I take it thats incorrect?
     
  20. clv101

    Capodecina

    Joined: 18 Oct 2002

    Posts: 10,739

    Location: Bristol

    no, of course it's right - the PSU will draw what the components in the system require plus a bit due to inefficiency. Use a 300W or 600W (of the same efficiency) on a system whose components only draw 100W and the total system consumption will be identical.