i'm doing about 2000 shares per kWh (only counting gpu consumption because the computer is on anyway). 1 kWh is 0.22 ($0.31) here. you need about 31000 shares per coin, so 15.5kWh or 3.41 (or $4.80).
edit
I'm running two miners with a power consumption of roughly 1300W, doing about 1.4BTC/day. 0.22/kwh =
1.3kw * (24h / 1.4BTC) * 0.22 =
4.90/BTC =~ 6.90$/BTC
Germany definitely isn't the best place for mining...
with your 2500Mhash/s, you should be doing about 2100 shares per hour, or at 1.3kW 1625 shares per kWh. that's 4.16 or $5.85. still not too great. 19kWh per btc is probably not the most efficient mining setup. did you increase the voltage on your 5830s? if yes, that's probably not efficient (in my case it's not), undo it. go with whatever clocks your stock voltage allows.