This doesn't seem to add up unless electricity over there costs a lot
more than over here!
100 watts in total, so 1 kilowatt hour (does everyone use these units?)
in 10 hours. In a month, 72 kilowatt hours. Over here, one kilowatt
hour costs about 5p or 0.05 UK pounds, so that makes 3.60 pounds per
month, or something like $6 (I don't know what the exchange rate is).