*Quote - You will use more power when reading/writing cd or dvd , and using the hard drive. Higher cpu use and memory changes all use a little more power.

A fast way to get a cost is to get the number of watts of your power supply (say 500 watts) and use that as killowatt hours which should be on your power bill. 500 watts is 0.5 Killowatts  so running for 1 hour is 0.5 KWH. My rate seems to be 29c per KWH so a computer costs 0.5 * 0.29 so call it 15 cents for the computer . Add the screen in the same way, and add peripherals like printers, modems etc which have thier own power supplies. That figure is the maximum cost.

a watt meter with recorder is the only way to tell actual use.

  Thanks,Ive looked on the power supply box and all I see is"Max output' 280 Watts ,is this then the figure I should base my calculation on?.

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