I split my hydro & natural gas with the family upstairs & the combined hydro for Nov & Dec was $187 & my share worked out to $75 for two months or $37.50/month
That has remained relatively stable over the last 2.5 years, even though I've since upgraded to 4 x 250w MH, and 4 x 90w (Sedra9000 pumps).
My 210g reef uses 19.5 kw/day so $1.20/day in electricity or $36/month.
According to that calculation, my computer, tv, house lights, stove, fridge & other tanks cost me only $1.50/month in extra electricity. Wow, that's awesome.
Anthony