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Thread: PC Annual Running Costs

  1. #1
    Automated Home Lurker
    Join Date
    Feb 2004

    Default PC Annual Running Costs

    Does anyone have any idea how much the electricity costs are to run a standard desktop PC for a year, 24 hours a day, 7 days a week?

    I plan to use a home automation server, which would be on all the time, although the monitor would be off. It would be on broadband connection & hard disk in use for video streaming.

    I know it can be worked out from the PC PSU power rating, however is the PC always using maximum power or does it depend what the PC is doing i.e. more power consumption to spin drives, CDs etc?

    Any info would be helpful, especially actual amounts that people have worked out from their electric bills.


    Crozzo 8)

  2. #2
    Automated Home Sr Member jon00's Avatar
    Join Date
    Jan 2004
    Bromley, UK

    Default Re: PC Annual Running Costs

    Well, I just got my meter out and measured one of my PC's for current consumption.

    (2 hard drives, 2 CD/DVD drives No monitor)

    Mains Voltage = 238V
    Computer current=0.55A

    Toyal wattage=131W or 0.131Kw (238 x 0.55)

    For 1 month = 0.131 x 24 x 31 = 97.46Kw

    For 1 year = 0.131 x24 x 365 = 1147.56Kw

    Say we choose a rate of 7.1 pence per unit (Kw/h):

    For 1 month 97.46 x 0.07 = 6.92

    For 1 year = 1147.56 x 0.071 = 81.48

    Obviously does not include any night units or standing charge values.

    Wow - and I have 4 PC's running 24/7!


  3. #3

    Default Re: PC Annual Running Costs

    Quick search of the UKHA_D mailing list turned up the below. Search for more at

    --- In ukha_d@xxxxxxx, "Marcus Warrington" <marcusw@m...>
    > On the subject of electricity usage I did a quick test the other
    > night. I checked the meter reading and I left my main PC
    > (Athlon1.4 + 7000rpm fan, 2 IDE 7200rpm discs, 19" Belinea Monitor)
    > on all night, then checked the meter, then left the PC off all
    > night and rechecked. Figures were 11.5 units used when PC was on
    > (10:30pm - 10am) compared to only 5 units used with PC off
    > (10:30pm - 8:30am).

    I hope I'm not teaching you to suck eggs here, but you can check
    consumption a lot faster than that if your electricity meter has one
    of those spinning discs in it.

    The discs rotate at a speed related to your rate of electricity
    consumption. Somewhere on the meter display will be marked how many
    revolutions per kilowatt-hour - I've seen meters with 400 revs per
    kWh and 266 revs per kWh, but there are probably others.

    Turn on the piece of kit you want to measure, then use a stopwatch to
    time how long each revolution of the disc takes. Then turn off the
    piece of kit, and repeat the measurement.

    You can then convert these measurements into rates of power
    consumption with some simple maths.

    For example:
    With your Mk III SuperDoobrey turned on each revolution of the disc
    takes twelve seconds. With it turned off, each revolution takes
    eighteen seconds. Your meter says 400 revs per kWh.

    There are 3600 seconds in an hour. With the Mk III SuperDoobrey on,
    twelve seconds per revolution is (3600/12=) 300 revolutions per hour.
    With 400 revs per kWh, your power consumption is (200/400=) 0.75
    kWh / h (ie 0.75 kW, or 750 watts).

    With the Mk III SuperDoobrey off, eighteen seconds per revolution is
    (3600/18=) 200 revolutions per hour. With 400 revs per kWh, your
    power consumption is (200/400=) 0.5 kWh / h (ie 0.5 kW, or 500 watts).

    The MkIII SuperDoobrey is therefore consuming 250 watts.


  4. #4
    Automated Home Lurker
    Join Date
    Apr 2004

    Default Re: PC Annual Running Costs

    Yes the activity of the PC dictates its power consumption.

    Say your PSU is rated @ 300 Watts, this will not be its regular power needs, this is the maximum.

    The maximum power draw on a PC is @ startup, as motors judder drives and fans into action and all the system components fire up.

    In your case (I assume) u r sending surveillance video to the drive. I also assume you are going to use motion detection software, so the drive could actually be allowed to spin down - it doesn't take an age to spin up again. Unless you want to send constant pics to a web front of your kitchen etc?

    Don't let it hibernate though, dependant on your system a burglar may get in and out before you get a pic of them :-(

    Have you thought of monitoring using an old low power PC?

    Anyhow, just to let you know that the PSU rating is not anywhere near the whole story.

    You could fit a meter to your PC as there are so many system and application dependant variables to consider - borrow one for a few days and multiply up to guesstimate your figure.

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