My old clunker at home uses about 150 watts per hour (w/o monitor, router etc).
Multiply this with 24 x 365 and you get the power consumption per year. Devide this value by 1,000 and you get kWh (kilo watt hours).
This kWh value gets multiplied with the price per kwh your utility is charging and you have the amount per year.

If I were running the above machine on a 24/7 basis, I would run up with about 240 EURO in engery cost alone.
Shared hosting is a lot less expensive.

You might search ebay for "Kill A Watt". I just got one of these devices a few weeks ago. It tells you the watts, amperage...

I've tested my server and it uses about 1 amp. So 1 amp multiplied by 120 volts = approx. 120 watts. Running for 1 hour, thats .12 kWHs.
For one day, that's 2.88 KWHs. For one month, that's 86.4 KWHs.

Now plug in your rate per KWH, and voila!

I guess my home server takes about $10/month to operate.

[edited by: encyclo at 10:41 am (utc) on Nov. 21, 2007]
[edit reason] no links to personal sites please [/edit]

$10/month is a good quickie estimate.

YMMV - less in Ontario. More in the nether regions of Alaska.

Or = one refrigerator.